diff --git a/dom/canvas/WebGL1Context.h b/dom/canvas/WebGL1Context.h
index d7d54265977c..b0c0ea7e66a1 100644
--- a/dom/canvas/WebGL1Context.h
+++ b/dom/canvas/WebGL1Context.h
@@ -31,6 +31,8 @@ public:
 
 private:
     virtual bool ValidateAttribPointerType(bool integerMode, GLenum type, GLsizei* alignment, const char* info) MOZ_OVERRIDE;
+    virtual bool ValidateBufferTarget(GLenum target, const char* info) MOZ_OVERRIDE;
+    virtual bool ValidateBufferIndexedTarget(GLenum target, const char* info) MOZ_OVERRIDE;
 };
 
 } // namespace mozilla
diff --git a/dom/canvas/WebGL1ContextBuffers.cpp b/dom/canvas/WebGL1ContextBuffers.cpp
new file mode 100644
index 000000000000..0a48d0b0801a
--- /dev/null
+++ b/dom/canvas/WebGL1ContextBuffers.cpp
@@ -0,0 +1,36 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "WebGL1Context.h"
+#include "WebGLBuffer.h"
+#include "GLContext.h"
+
+using namespace mozilla;
+using namespace mozilla::dom;
+
+// -------------------------------------------------------------------------
+// Buffer objects
+
+/** Target validation for BindBuffer, etc */
+bool
+WebGL1Context::ValidateBufferTarget(GLenum target, const char* info)
+{
+    switch (target) {
+    case LOCAL_GL_ARRAY_BUFFER:
+    case LOCAL_GL_ELEMENT_ARRAY_BUFFER:
+        return true;
+
+    default:
+        ErrorInvalidEnumInfo(info, target);
+        return false;
+    }
+}
+
+bool
+WebGL1Context::ValidateBufferIndexedTarget(GLenum target, const char* info)
+{
+    ErrorInvalidEnumInfo(info, target);
+    return false;
+}
diff --git a/dom/canvas/WebGL2Context.cpp b/dom/canvas/WebGL2Context.cpp
index 0bba0aec2717..f8884eafbe6f 100644
--- a/dom/canvas/WebGL2Context.cpp
+++ b/dom/canvas/WebGL2Context.cpp
@@ -6,6 +6,8 @@
 #include "WebGL2Context.h"
 
 #include "GLContext.h"
+#include "WebGLBuffer.h"
+#include "WebGLTransformFeedback.h"
 #include "mozilla/dom/WebGL2RenderingContextBinding.h"
 #include "mozilla/Preferences.h"
 #include "mozilla/Telemetry.h"
@@ -117,6 +119,11 @@ WebGLContext::InitWebGL2()
     gl->GetUIntegerv(LOCAL_GL_MAX_TRANSFORM_FEEDBACK_SEPARATE_ATTRIBS,
                      &mGLMaxTransformFeedbackSeparateAttribs);
 
+    mDefaultTransformFeedback = new WebGLTransformFeedback(this, 0);
+    mBoundTransformFeedback = mDefaultTransformFeedback;
+    auto xfBuffers = new WebGLRefPtr<WebGLBuffer>[mGLMaxTransformFeedbackSeparateAttribs];
+    mBoundTransformFeedbackBuffers.reset(xfBuffers);
+
     return true;
 }
 
diff --git a/dom/canvas/WebGL2Context.h b/dom/canvas/WebGL2Context.h
index 416390886a0a..680ab9a54bcb 100644
--- a/dom/canvas/WebGL2Context.h
+++ b/dom/canvas/WebGL2Context.h
@@ -215,14 +215,13 @@ public:
     already_AddRefed<WebGLTransformFeedback> CreateTransformFeedback();
     void DeleteTransformFeedback(WebGLTransformFeedback* tf);
     bool IsTransformFeedback(WebGLTransformFeedback* tf);
-    void BindTransformFeedback(GLenum target, GLuint id);
+    void BindTransformFeedback(GLenum target, WebGLTransformFeedback* tf);
     void BeginTransformFeedback(GLenum primitiveMode);
     void EndTransformFeedback();
-    void TransformFeedbackVaryings(WebGLProgram* program, GLsizei count,
-                                   const dom::Sequence<nsString>& varyings, GLenum bufferMode);
-    already_AddRefed<WebGLActiveInfo> GetTransformFeedbackVarying(WebGLProgram* program, GLuint index);
     void PauseTransformFeedback();
     void ResumeTransformFeedback();
+    void TransformFeedbackVaryings(WebGLProgram* program, const dom::Sequence<nsString>& varyings, GLenum bufferMode);
+    already_AddRefed<WebGLActiveInfo> GetTransformFeedbackVarying(WebGLProgram* program, GLuint index);
 
 
     // -------------------------------------------------------------------------
@@ -263,6 +262,8 @@ private:
                                 const char* info);
 
     virtual bool ValidateAttribPointerType(bool integerMode, GLenum type, GLsizei* alignment, const char* info) MOZ_OVERRIDE;
+    virtual bool ValidateBufferTarget(GLenum target, const char* info) MOZ_OVERRIDE;
+    virtual bool ValidateBufferIndexedTarget(GLenum target, const char* info) MOZ_OVERRIDE;
 };
 
 } // namespace mozilla
diff --git a/dom/canvas/WebGL2ContextBuffers.cpp b/dom/canvas/WebGL2ContextBuffers.cpp
index 41e12b4af43f..8c7f75137440 100644
--- a/dom/canvas/WebGL2ContextBuffers.cpp
+++ b/dom/canvas/WebGL2ContextBuffers.cpp
@@ -9,6 +9,35 @@
 using namespace mozilla;
 using namespace mozilla::dom;
 
+bool
+WebGL2Context::ValidateBufferTarget(GLenum target, const char* info)
+{
+    switch (target) {
+    case LOCAL_GL_ARRAY_BUFFER:
+    case LOCAL_GL_ELEMENT_ARRAY_BUFFER:
+    case LOCAL_GL_TRANSFORM_FEEDBACK_BUFFER:
+        return true;
+
+    default:
+        ErrorInvalidEnumInfo(info, target);
+        return false;
+    }
+}
+
+bool
+WebGL2Context::ValidateBufferIndexedTarget(GLenum target, const char* info)
+{
+    switch (target) {
+    case LOCAL_GL_TRANSFORM_FEEDBACK_BUFFER:
+    case LOCAL_GL_UNIFORM_BUFFER:
+        return true;
+
+    default:
+        ErrorInvalidEnumInfo(info, target);
+        return false;
+    }
+}
+
 // -------------------------------------------------------------------------
 // Buffer objects
 
diff --git a/dom/canvas/WebGL2ContextTransformFeedback.cpp b/dom/canvas/WebGL2ContextTransformFeedback.cpp
index 37ced46c7891..76a960786fcd 100644
--- a/dom/canvas/WebGL2ContextTransformFeedback.cpp
+++ b/dom/canvas/WebGL2ContextTransformFeedback.cpp
@@ -4,6 +4,9 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 #include "WebGL2Context.h"
+#include "WebGLActiveInfo.h"
+#include "WebGLProgram.h"
+#include "WebGLTransformFeedback.h"
 #include "GLContext.h"
 
 using namespace mozilla;
@@ -15,64 +18,237 @@ using namespace mozilla::dom;
 already_AddRefed<WebGLTransformFeedback>
 WebGL2Context::CreateTransformFeedback()
 {
-    MOZ_CRASH("Not Implemented.");
-    return nullptr;
+    if (IsContextLost())
+        return nullptr;
+
+    GLuint tf = 0;
+    MakeContextCurrent();
+    gl->fGenTransformFeedbacks(1, &tf);
+
+    nsRefPtr<WebGLTransformFeedback> globj = new WebGLTransformFeedback(this, tf);
+    return globj.forget();
 }
 
 void
 WebGL2Context::DeleteTransformFeedback(WebGLTransformFeedback* tf)
 {
-    MOZ_CRASH("Not Implemented.");
+    if (IsContextLost())
+        return;
+
+    if (!ValidateObjectAllowDeletedOrNull("deleteTransformFeedback", tf))
+        return;
+
+    if (!tf || tf->IsDeleted())
+        return;
+
+    if (mBoundTransformFeedback == tf)
+        BindTransformFeedback(LOCAL_GL_TRANSFORM_FEEDBACK, tf);
+
+    tf->RequestDelete();
 }
 
 bool
 WebGL2Context::IsTransformFeedback(WebGLTransformFeedback* tf)
 {
-    MOZ_CRASH("Not Implemented.");
-    return false;
+    if (IsContextLost())
+        return false;
+
+    if (!ValidateObjectAllowDeleted("isTransformFeedback", tf))
+        return false;
+
+    if (tf->IsDeleted())
+        return false;
+
+    MakeContextCurrent();
+    return gl->fIsTransformFeedback(tf->GLName());
 }
 
 void
-WebGL2Context::BindTransformFeedback(GLenum target, GLuint id)
+WebGL2Context::BindTransformFeedback(GLenum target, WebGLTransformFeedback* tf)
 {
-    MOZ_CRASH("Not Implemented.");
+    if (IsContextLost())
+        return;
+
+    if (!ValidateObjectAllowDeletedOrNull("bindTransformFeedback", tf))
+        return;
+
+    if (target != LOCAL_GL_TRANSFORM_FEEDBACK)
+        return ErrorInvalidEnum("bindTransformFeedback: target must be TRANSFORM_FEEDBACK");
+
+    WebGLRefPtr<WebGLTransformFeedback> currentTF = mBoundTransformFeedback;
+    if (currentTF && currentTF->mIsActive && !currentTF->mIsPaused) {
+        return ErrorInvalidOperation("bindTransformFeedback: Currently bound transform "
+                                     "feedback is active and not paused");
+    }
+
+    if (tf && tf->IsDeleted())
+        return ErrorInvalidOperation("bindTransformFeedback: Attempt to bind deleted id");
+
+    if (tf)
+        tf->BindTo(LOCAL_GL_TRANSFORM_FEEDBACK);
+
+    MakeContextCurrent();
+    gl->fBindTransformFeedback(target, tf ? tf->GLName() : 0);
+    if (tf)
+        mBoundTransformFeedback = tf;
+    else
+        mBoundTransformFeedback = mDefaultTransformFeedback;
 }
 
 void
 WebGL2Context::BeginTransformFeedback(GLenum primitiveMode)
 {
-    MOZ_CRASH("Not Implemented.");
+    if (IsContextLost())
+        return;
+
+    WebGLTransformFeedback* tf = mBoundTransformFeedback;
+    MOZ_ASSERT(tf);
+    if (!tf)
+        return;
+
+    if (tf->mIsActive)
+        return ErrorInvalidOperation("beginTransformFeedback: transform feedback is active");
+
+    const GLenum mode = tf->mMode;
+    if (mode != LOCAL_GL_POINTS && mode != LOCAL_GL_LINES && mode != LOCAL_GL_TRIANGLES)
+        return ErrorInvalidEnum("beginTransformFeedback: primitive must be one of POINTS, LINES, or TRIANGLES");
+
+    // TODO:
+    // GL_INVALID_OPERATION is generated by glBeginTransformFeedback
+    // if any binding point used in transform feedback mode does not
+    // have a buffer object bound. In interleaved mode, only the first
+    // buffer object binding point is ever written to.
+
+    // GL_INVALID_OPERATION is generated by glBeginTransformFeedback
+    // if no binding points would be used, either because no program
+    // object is active of because the active program object has
+    // specified no varying variables to record.
+    if (!mCurrentProgram)
+        return ErrorInvalidOperation("beginTransformFeedback: no program is active");
+
+    MakeContextCurrent();
+    gl->fBeginTransformFeedback(primitiveMode);
+    tf->mIsActive = true;
+    tf->mIsPaused = false;
 }
 
 void
 WebGL2Context::EndTransformFeedback()
 {
-    MOZ_CRASH("Not Implemented.");
+    if (IsContextLost())
+        return;
+
+    WebGLTransformFeedback* tf = mBoundTransformFeedback;
+    MOZ_ASSERT(tf);
+
+    if (!tf)
+        return;
+
+    if (!tf->mIsActive)
+        return ErrorInvalidOperation("%s: transform feedback in not active",
+                                     "endTransformFeedback");
+
+    MakeContextCurrent();
+    gl->fEndTransformFeedback();
+    tf->mIsActive = false;
+    tf->mIsPaused = false;
 }
 
 void
-WebGL2Context::TransformFeedbackVaryings(WebGLProgram* program, GLsizei count,
-                                         const dom::Sequence<nsString>& varyings, GLenum bufferMode)
+WebGL2Context::PauseTransformFeedback()
 {
-    MOZ_CRASH("Not Implemented.");
+    if (IsContextLost())
+        return;
+
+    WebGLTransformFeedback* tf = mBoundTransformFeedback;
+    MOZ_ASSERT(tf);
+    if (!tf)
+        return;
+
+    if (!tf->mIsActive || tf->mIsPaused) {
+        return ErrorInvalidOperation("%s: transform feedback is not active or is paused",
+                                     "pauseTransformFeedback");
+    }
+
+    MakeContextCurrent();
+    gl->fPauseTransformFeedback();
+    tf->mIsPaused = true;
+}
+
+void
+WebGL2Context::ResumeTransformFeedback()
+{
+    if (IsContextLost())
+        return;
+
+    WebGLTransformFeedback* tf = mBoundTransformFeedback;
+    MOZ_ASSERT(tf);
+    if (!tf)
+        return;
+
+    if (!tf->mIsActive || !tf->mIsPaused)
+        return ErrorInvalidOperation("resumeTransformFeedback: transform feedback is not active or is not paused");
+
+    MakeContextCurrent();
+    gl->fResumeTransformFeedback();
+    tf->mIsPaused = false;
+}
+
+void
+WebGL2Context::TransformFeedbackVaryings(WebGLProgram* program,
+                                         const dom::Sequence<nsString>& varyings,
+                                         GLenum bufferMode)
+{
+    if (IsContextLost())
+        return;
+
+    if (!ValidateObject("transformFeedbackVaryings: program", program))
+        return;
+
+    GLsizei count = varyings.Length();
+    GLchar** tmpVaryings = (GLchar**) nsMemory::Alloc(count * sizeof(GLchar*));
+
+    for (GLsizei n = 0; n < count; n++) {
+        tmpVaryings[n] = (GLchar*) ToNewCString(varyings[n]);
+    }
+
+    GLuint progname = program->GLName();
+    MakeContextCurrent();
+    gl->fTransformFeedbackVaryings(progname, count, tmpVaryings, bufferMode);
+
+    NS_FREE_XPCOM_ALLOCATED_POINTER_ARRAY(count, tmpVaryings);
 }
 
 
 already_AddRefed<WebGLActiveInfo>
 WebGL2Context::GetTransformFeedbackVarying(WebGLProgram* program, GLuint index)
 {
-    MOZ_CRASH("Not Implemented.");
-    return nullptr;
-}
+    if (IsContextLost())
+        return nullptr;
 
-void
-WebGL2Context::PauseTransformFeedback()
-{
-    MOZ_CRASH("Not Implemented.");
-}
+    if (!ValidateObject("getTransformFeedbackVarying: program", program))
+        return nullptr;
 
-void
-WebGL2Context::ResumeTransformFeedback()
-{
-    MOZ_CRASH("Not Implemented.");
+    MakeContextCurrent();
+
+    GLint len = 0;
+    GLuint progname = program->GLName();
+    gl->fGetProgramiv(progname, LOCAL_GL_TRANSFORM_FEEDBACK_VARYING_MAX_LENGTH, &len);
+    if (!len)
+        return nullptr;
+
+    UniquePtr<char[]> name(new char[len]);
+    GLint tfsize = 0;
+    GLuint tftype = 0;
+
+    gl->fGetTransformFeedbackVarying(progname, index, len, &len, &tfsize, &tftype, name.get());
+    if (len == 0 || tfsize == 0 || tftype == 0)
+        return nullptr;
+
+    // TODO(djg): Reverse lookup of name
+    // nsCString reverseMappedName;
+    // prog->ReverveMapIdentifier(nsDependentCString(name), &reverseMappedName);
+
+    nsRefPtr<WebGLActiveInfo> result = new WebGLActiveInfo(tfsize, tftype, nsDependentCString(name.get()));
+    return result.forget();
 }
diff --git a/dom/canvas/WebGLContext.cpp b/dom/canvas/WebGLContext.cpp
index 9354bb5beb72..0bb54d2cd924 100644
--- a/dom/canvas/WebGLContext.cpp
+++ b/dom/canvas/WebGLContext.cpp
@@ -54,6 +54,7 @@
 #include "WebGLObjectModel.h"
 #include "WebGLQuery.h"
 #include "WebGLSampler.h"
+#include "WebGLTransformFeedback.h"
 #include "WebGLVertexArray.h"
 #include "WebGLVertexAttribData.h"
 
@@ -328,6 +329,14 @@ WebGLContext::DestroyResourcesAndContext()
     mBoundRenderbuffer = nullptr;
     mBoundVertexArray = nullptr;
     mDefaultVertexArray = nullptr;
+    mBoundTransformFeedback = nullptr;
+    mDefaultTransformFeedback = nullptr;
+
+    if (mBoundTransformFeedbackBuffers) {
+        for (GLuint i = 0; i < mGLMaxTransformFeedbackSeparateAttribs; i++) {
+            mBoundTransformFeedbackBuffers[i] = nullptr;
+        }
+    }
 
     while (!mTextures.isEmpty())
         mTextures.getLast()->DeleteOnce();
@@ -347,6 +356,8 @@ WebGLContext::DestroyResourcesAndContext()
         mQueries.getLast()->DeleteOnce();
     while (!mSamplers.isEmpty())
         mSamplers.getLast()->DeleteOnce();
+    while (!mTransformFeedbacks.isEmpty())
+        mTransformFeedbacks.getLast()->DeleteOnce();
 
     mBlackOpaqueTexture2D = nullptr;
     mBlackOpaqueTextureCubeMap = nullptr;
diff --git a/dom/canvas/WebGLContext.h b/dom/canvas/WebGLContext.h
index dbeab2963346..5c426b9ccd9b 100644
--- a/dom/canvas/WebGLContext.h
+++ b/dom/canvas/WebGLContext.h
@@ -80,6 +80,7 @@ class WebGLSampler;
 class WebGLShader;
 class WebGLShaderPrecisionFormat;
 class WebGLTexture;
+class WebGLTransformFeedback;
 class WebGLUniformLocation;
 class WebGLVertexArray;
 struct WebGLVertexAttribData;
@@ -881,19 +882,16 @@ public:
     void DeleteBuffer(WebGLBuffer* buf);
     bool IsBuffer(WebGLBuffer* buf);
 
-private:
-    // ARRAY_BUFFER slot
+protected:
+    // bound buffer state
     WebGLRefPtr<WebGLBuffer> mBoundArrayBuffer;
-
-    // TRANSFORM_FEEDBACK_BUFFER slot
     WebGLRefPtr<WebGLBuffer> mBoundTransformFeedbackBuffer;
 
-    // these two functions emit INVALID_ENUM for invalid `target`.
-    WebGLRefPtr<WebGLBuffer>* GetBufferSlotByTarget(GLenum target,
-                                                    const char* info);
+    UniquePtr<WebGLRefPtr<WebGLBuffer>[]> mBoundTransformFeedbackBuffers;
+
+    WebGLRefPtr<WebGLBuffer>* GetBufferSlotByTarget(GLenum target);
     WebGLRefPtr<WebGLBuffer>* GetBufferSlotByTargetIndexed(GLenum target,
-                                                           GLuint index,
-                                                           const char* info);
+                                                           GLuint index);
     bool ValidateBufferUsageEnum(GLenum target, const char* info);
 
 // -----------------------------------------------------------------------------
@@ -1114,7 +1112,7 @@ protected:
     int32_t mGLMaxVertexUniformVectors;
     int32_t mGLMaxColorAttachments;
     int32_t mGLMaxDrawBuffers;
-    uint32_t mGLMaxTransformFeedbackSeparateAttribs;
+    GLuint  mGLMaxTransformFeedbackSeparateAttribs;
 
 public:
     GLuint MaxVertexAttribs() const {
@@ -1339,6 +1337,8 @@ private:
     // -------------------------------------------------------------------------
     // Context customization points
     virtual bool ValidateAttribPointerType(bool integerMode, GLenum type, GLsizei* alignment, const char* info) = 0;
+    virtual bool ValidateBufferTarget(GLenum target, const char* info) = 0;
+    virtual bool ValidateBufferIndexedTarget(GLenum target, const char* info) = 0;
 
 protected:
     int32_t MaxTextureSizeForTarget(TexTarget target) const {
@@ -1380,6 +1380,7 @@ protected:
 
     WebGLRefPtr<WebGLFramebuffer> mBoundFramebuffer;
     WebGLRefPtr<WebGLRenderbuffer> mBoundRenderbuffer;
+    WebGLRefPtr<WebGLTransformFeedback> mBoundTransformFeedback;
     WebGLRefPtr<WebGLVertexArray> mBoundVertexArray;
 
     LinkedList<WebGLTexture> mTextures;
@@ -1393,8 +1394,10 @@ protected:
 
     // TODO(djg): Does this need a rethink? Should it be WebGL2Context?
     LinkedList<WebGLSampler> mSamplers;
+    LinkedList<WebGLTransformFeedback> mTransformFeedbacks;
 
     WebGLRefPtr<WebGLVertexArray> mDefaultVertexArray;
+    WebGLRefPtr<WebGLTransformFeedback> mDefaultTransformFeedback;
 
     // PixelStore parameters
     uint32_t mPixelStorePackAlignment;
@@ -1518,6 +1521,7 @@ public:
     friend class WebGLBuffer;
     friend class WebGLSampler;
     friend class WebGLShader;
+    friend class WebGLTransformFeedback;
     friend class WebGLUniformLocation;
     friend class WebGLVertexArray;
     friend class WebGLVertexArrayFake;
diff --git a/dom/canvas/WebGLContextBuffers.cpp b/dom/canvas/WebGLContextBuffers.cpp
index 32013428555f..7724b7e07665 100644
--- a/dom/canvas/WebGLContextBuffers.cpp
+++ b/dom/canvas/WebGLContextBuffers.cpp
@@ -24,11 +24,12 @@ WebGLContext::BindBuffer(GLenum target, WebGLBuffer* buffer)
     if (buffer && buffer->IsDeleted())
         return;
 
-    WebGLRefPtr<WebGLBuffer>* bufferSlot = GetBufferSlotByTarget(target,
-                                                                 "bindBuffer");
-    if (!bufferSlot)
+    if (!ValidateBufferTarget(target, "bindBuffer"))
         return;
 
+    WebGLRefPtr<WebGLBuffer>* bufferSlot = GetBufferSlotByTarget(target);
+    MOZ_ASSERT(bufferSlot);
+
     if (buffer) {
         if (!buffer->HasEverBeenBound()) {
             buffer->BindTo(target);
@@ -60,11 +61,19 @@ WebGLContext::BindBufferBase(GLenum target, GLuint index, WebGLBuffer* buffer)
         return;
     }
 
+    // ValidateBufferTarget
+    switch (target) {
+    case LOCAL_GL_TRANSFORM_FEEDBACK_BUFFER:
+        if (index >= mGLMaxTransformFeedbackSeparateAttribs)
+            return ErrorInvalidValue("bindBufferBase: index should be less than "
+                                     "MAX_TRANSFORM_FEEDBACK_SEPARATE_ATTRIBS");
+    default:
+        return ErrorInvalidEnumInfo("bindBufferBase: target", target);
+    }
+
     WebGLRefPtr<WebGLBuffer>* indexedBufferSlot;
-    indexedBufferSlot = GetBufferSlotByTargetIndexed(target, index,
-                                                     "bindBufferBase");
-    if (!indexedBufferSlot)
-        return;
+    indexedBufferSlot = GetBufferSlotByTargetIndexed(target, index);
+    MOZ_ASSERT(indexedBufferSlot);
 
     if (buffer) {
         if (!buffer->HasEverBeenBound())
@@ -77,9 +86,7 @@ WebGLContext::BindBufferBase(GLenum target, GLuint index, WebGLBuffer* buffer)
         }
     }
 
-    WebGLRefPtr<WebGLBuffer>* bufferSlot = GetBufferSlotByTarget(target,
-                                                                 "bindBufferBase");
-
+    WebGLRefPtr<WebGLBuffer>* bufferSlot = GetBufferSlotByTarget(target);
     MOZ_ASSERT(bufferSlot, "GetBufferSlotByTarget(Indexed) mismatch");
 
     *indexedBufferSlot = buffer;
@@ -104,11 +111,20 @@ WebGLContext::BindBufferRange(GLenum target, GLuint index, WebGLBuffer* buffer,
     if (buffer && buffer->IsDeleted())
         return;
 
+    // ValidateBufferTarget
+    switch (target) {
+    case LOCAL_GL_TRANSFORM_FEEDBACK_BUFFER:
+        if (index >= mGLMaxTransformFeedbackSeparateAttribs)
+            return ErrorInvalidValue("bindBufferRange: index should be less than "
+                                     "MAX_TRANSFORM_FEEDBACK_SEPARATE_ATTRIBS");
+
+    default:
+        return ErrorInvalidEnumInfo("bindBufferRange: target", target);
+    }
+
     WebGLRefPtr<WebGLBuffer>* indexedBufferSlot;
-    indexedBufferSlot = GetBufferSlotByTargetIndexed(target, index,
-                                                     "bindBufferRange");
-    if (!indexedBufferSlot)
-        return;
+    indexedBufferSlot = GetBufferSlotByTargetIndexed(target, index);
+    MOZ_ASSERT(indexedBufferSlot);
 
     if (buffer) {
         if (!buffer->HasEverBeenBound())
@@ -128,9 +144,7 @@ WebGLContext::BindBufferRange(GLenum target, GLuint index, WebGLBuffer* buffer,
         }
     }
 
-    WebGLRefPtr<WebGLBuffer>* bufferSlot = GetBufferSlotByTarget(target,
-                                                                 "BindBufferRange");
-
+    WebGLRefPtr<WebGLBuffer>* bufferSlot = GetBufferSlotByTarget(target);
     MOZ_ASSERT(bufferSlot, "GetBufferSlotByTarget(Indexed) mismatch");
 
     *indexedBufferSlot = buffer;
@@ -148,11 +162,12 @@ WebGLContext::BufferData(GLenum target, WebGLsizeiptr size, GLenum usage)
     if (IsContextLost())
         return;
 
-    WebGLRefPtr<WebGLBuffer>* bufferSlot = GetBufferSlotByTarget(target,
-                                                                 "bufferData");
-    if (!bufferSlot)
+    if (!ValidateBufferTarget(target, "bufferData"))
         return;
 
+    WebGLRefPtr<WebGLBuffer>* bufferSlot = GetBufferSlotByTarget(target);
+    MOZ_ASSERT(bufferSlot);
+
     if (size < 0)
         return ErrorInvalidValue("bufferData: negative size");
 
@@ -201,11 +216,12 @@ WebGLContext::BufferData(GLenum target,
         return ErrorInvalidValue("bufferData: null object passed");
     }
 
-    WebGLRefPtr<WebGLBuffer>* bufferSlot = GetBufferSlotByTarget(target,
-                                                                 "bufferData");
-    if (!bufferSlot)
+    if (!ValidateBufferTarget(target, "bufferData"))
         return;
 
+    WebGLRefPtr<WebGLBuffer>* bufferSlot = GetBufferSlotByTarget(target);
+    MOZ_ASSERT(bufferSlot);
+
     const dom::ArrayBuffer& data = maybeData.Value();
     data.ComputeLengthAndData();
 
@@ -244,11 +260,12 @@ WebGLContext::BufferData(GLenum target, const dom::ArrayBufferView& data,
     if (IsContextLost())
         return;
 
-    WebGLRefPtr<WebGLBuffer>* bufferSlot = GetBufferSlotByTarget(target,
-                                                                 "bufferSubData");
-    if (!bufferSlot)
+    if (!ValidateBufferTarget(target, "bufferData"))
         return;
 
+    WebGLRefPtr<WebGLBuffer>* bufferSlot = GetBufferSlotByTarget(target);
+    MOZ_ASSERT(bufferSlot);
+
     if (!ValidateBufferUsageEnum(usage, "bufferData: usage"))
         return;
 
@@ -290,11 +307,12 @@ WebGLContext::BufferSubData(GLenum target, WebGLsizeiptr byteOffset,
         return;
     }
 
-    WebGLRefPtr<WebGLBuffer>* bufferSlot = GetBufferSlotByTarget(target,
-                                                                 "bufferSubData");
-    if (!bufferSlot)
+    if (!ValidateBufferTarget(target, "bufferSubData"))
         return;
 
+    WebGLRefPtr<WebGLBuffer>* bufferSlot = GetBufferSlotByTarget(target);
+    MOZ_ASSERT(bufferSlot);
+
     if (byteOffset < 0)
         return ErrorInvalidValue("bufferSubData: negative offset");
 
@@ -335,11 +353,12 @@ WebGLContext::BufferSubData(GLenum target, WebGLsizeiptr byteOffset,
     if (IsContextLost())
         return;
 
-    WebGLRefPtr<WebGLBuffer>* bufferSlot = GetBufferSlotByTarget(target,
-                                                                 "bufferSubData");
-    if (!bufferSlot)
+    if (!ValidateBufferTarget(target, "bufferSubData"))
         return;
 
+    WebGLRefPtr<WebGLBuffer>* bufferSlot = GetBufferSlotByTarget(target);
+    MOZ_ASSERT(bufferSlot);
+
     if (byteOffset < 0)
         return ErrorInvalidValue("bufferSubData: negative offset");
 
@@ -445,48 +464,35 @@ WebGLContext::ValidateBufferUsageEnum(GLenum target, const char* info)
 }
 
 WebGLRefPtr<WebGLBuffer>*
-WebGLContext::GetBufferSlotByTarget(GLenum target, const char* info)
+WebGLContext::GetBufferSlotByTarget(GLenum target)
 {
+    /* This function assumes that target has been validated for either WebGL1 or WebGL. */
     switch (target) {
-    case LOCAL_GL_ARRAY_BUFFER:
-        return &mBoundArrayBuffer;
+        case LOCAL_GL_ARRAY_BUFFER:
+            return &mBoundArrayBuffer;
 
-    case LOCAL_GL_ELEMENT_ARRAY_BUFFER:
-        return &mBoundVertexArray->mElementArrayBuffer;
+        case LOCAL_GL_ELEMENT_ARRAY_BUFFER:
+            return &mBoundVertexArray->mElementArrayBuffer;
 
-    case LOCAL_GL_TRANSFORM_FEEDBACK_BUFFER:
-        if (!IsWebGL2()) {
-            break;
-        }
-        return &mBoundTransformFeedbackBuffer;
+        case LOCAL_GL_TRANSFORM_FEEDBACK_BUFFER:
+            return &mBoundTransformFeedbackBuffer;
 
-    default:
-        break;
+        default:
+            return nullptr;
     }
-
-    ErrorInvalidEnum("%s: target: Invalid enum value 0x%x.", info, target);
-    return nullptr;
 }
 
 WebGLRefPtr<WebGLBuffer>*
-WebGLContext::GetBufferSlotByTargetIndexed(GLenum target, GLuint index,
-                                           const char* info)
+WebGLContext::GetBufferSlotByTargetIndexed(GLenum target, GLuint index)
 {
+    /* This function assumes that target has been validated for either WebGL1 or WebGL. */
     switch (target) {
     case LOCAL_GL_TRANSFORM_FEEDBACK_BUFFER:
-        if (index >= mGLMaxTransformFeedbackSeparateAttribs) {
-            ErrorInvalidValue("%s: `index` should be less than"
-                              " MAX_TRANSFORM_FEEDBACK_SEPARATE_ATTRIBS.", info,
-                              index);
-            return nullptr;
-        }
-        return nullptr; // See bug 903594
-
-    default:
-        break;
+        MOZ_ASSERT(index < mGLMaxTransformFeedbackSeparateAttribs);
+        return &mBoundTransformFeedbackBuffers[index];
     }
 
-    ErrorInvalidEnum("%s: target: invalid enum value 0x%x", info, target);
+    MOZ_CRASH("Should not get here.");
     return nullptr;
 }
 
diff --git a/dom/canvas/WebGLContextGL.cpp b/dom/canvas/WebGLContextGL.cpp
index 47d840908d7b..08d935a2c069 100644
--- a/dom/canvas/WebGLContextGL.cpp
+++ b/dom/canvas/WebGLContextGL.cpp
@@ -1105,12 +1105,12 @@ WebGLContext::GetBufferParameter(GLenum target, GLenum pname)
     if (IsContextLost())
         return JS::NullValue();
 
-
-    WebGLRefPtr<WebGLBuffer>* slot = GetBufferSlotByTarget(target,
-                                                           "getBufferParameter");
-    if (!slot)
+    if (!ValidateBufferTarget(target, "getBufferParameter"))
         return JS::NullValue();
 
+    WebGLRefPtr<WebGLBuffer>* slot = GetBufferSlotByTarget(target);
+    MOZ_ASSERT(slot);
+
     if (!*slot) {
         ErrorInvalidOperation("No buffer bound to `target` (0x%4x).", target);
         return JS::NullValue();
diff --git a/dom/canvas/WebGLTransformFeedback.cpp b/dom/canvas/WebGLTransformFeedback.cpp
index bd950e246ae7..283c9610d7ac 100644
--- a/dom/canvas/WebGLTransformFeedback.cpp
+++ b/dom/canvas/WebGLTransformFeedback.cpp
@@ -11,27 +11,37 @@
 
 namespace mozilla {
 
-WebGLTransformFeedback::WebGLTransformFeedback(WebGLContext* webgl)
-    : WebGLBindableName<GLenum>(0)
-    , WebGLContextBoundObject(webgl)
+WebGLTransformFeedback::WebGLTransformFeedback(WebGLContext* context,
+                                               GLuint tf)
+    : WebGLBindableName<GLenum>(tf)
+    , WebGLContextBoundObject(context)
+    , mMode(LOCAL_GL_NONE)
+    , mIsActive(false)
+    , mIsPaused(false)
 {
-    MOZ_CRASH("Not Implemented.");
+    context->mTransformFeedbacks.insertBack(this);
 }
 
 WebGLTransformFeedback::~WebGLTransformFeedback()
-{}
+{
+    mMode = LOCAL_GL_NONE;
+    mIsActive = false;
+    mIsPaused = false;
+    DeleteOnce();
+}
 
 void
 WebGLTransformFeedback::Delete()
 {
-    MOZ_CRASH("Not Implemented.");
+    mContext->MakeContextCurrent();
+    mContext->gl->fDeleteTransformFeedbacks(1, &mGLName);
+    removeFrom(mContext->mTransformFeedbacks);
 }
 
 WebGLContext*
 WebGLTransformFeedback::GetParentObject() const
 {
-    MOZ_CRASH("Not Implemented.");
-    return nullptr;
+    return Context();
 }
 
 JSObject*
diff --git a/dom/canvas/WebGLTransformFeedback.h b/dom/canvas/WebGLTransformFeedback.h
index cd079f10c14a..5c16276f326c 100644
--- a/dom/canvas/WebGLTransformFeedback.h
+++ b/dom/canvas/WebGLTransformFeedback.h
@@ -21,9 +21,10 @@ class WebGLTransformFeedback MOZ_FINAL
     , public WebGLContextBoundObject
 {
     friend class WebGLContext;
+    friend class WebGL2Context;
 
 public:
-    explicit WebGLTransformFeedback(WebGLContext* webgl);
+    explicit WebGLTransformFeedback(WebGLContext* webgl, GLuint tf);
 
     void Delete();
     WebGLContext* GetParentObject() const;
@@ -34,6 +35,9 @@ public:
 
 private:
     ~WebGLTransformFeedback();
+    GLenum mMode;
+    bool mIsActive;
+    bool mIsPaused;
 };
 
 } // namespace mozilla
diff --git a/dom/canvas/moz.build b/dom/canvas/moz.build
index 5c7d32438ae5..0c85a2c4e0b6 100644
--- a/dom/canvas/moz.build
+++ b/dom/canvas/moz.build
@@ -42,6 +42,7 @@ UNIFIED_SOURCES += [
 UNIFIED_SOURCES += [
     'MurmurHash3.cpp',
     'WebGL1Context.cpp',
+    'WebGL1ContextBuffers.cpp',
     'WebGL1ContextUniforms.cpp',
     'WebGL2Context.cpp',
     'WebGL2ContextBuffers.cpp',
diff --git a/dom/webidl/WebGL2RenderingContext.webidl b/dom/webidl/WebGL2RenderingContext.webidl
index 6b950dcfe462..b981883d7146 100644
--- a/dom/webidl/WebGL2RenderingContext.webidl
+++ b/dom/webidl/WebGL2RenderingContext.webidl
@@ -443,10 +443,10 @@ interface WebGL2RenderingContext : WebGLRenderingContext
     WebGLTransformFeedback? createTransformFeedback();
     void deleteTransformFeedback(WebGLTransformFeedback? tf);
     [WebGLHandlesContextLoss] GLboolean isTransformFeedback(WebGLTransformFeedback? tf);
-    void bindTransformFeedback(GLenum target, GLuint id);
+    void bindTransformFeedback(GLenum target, WebGLTransformFeedback? tf);
     void beginTransformFeedback(GLenum primitiveMode);
     void endTransformFeedback();
-    void transformFeedbackVaryings(WebGLProgram? program, GLsizei count, sequence<DOMString> varyings, GLenum bufferMode);
+    void transformFeedbackVaryings(WebGLProgram? program, sequence<DOMString> varyings, GLenum bufferMode);
     [NewObject] WebGLActiveInfo? getTransformFeedbackVarying(WebGLProgram? program, GLuint index);
     void pauseTransformFeedback();
     void resumeTransformFeedback();
diff --git a/gfx/gl/GLContext.h b/gfx/gl/GLContext.h
index dfa9ea0de674..4d6a04db1ca1 100644
--- a/gfx/gl/GLContext.h
+++ b/gfx/gl/GLContext.h
@@ -2730,7 +2730,7 @@ public:
         AFTER_GL_CALL;
     }
 
-    void fDeleteTransformFeedbacks(GLsizei n, GLuint* ids)
+    void fDeleteTransformFeedbacks(GLsizei n, const GLuint* ids)
     {
         BEFORE_GL_CALL;
         ASSERT_SYMBOL_PRESENT(fDeleteTransformFeedbacks);
diff --git a/gfx/gl/GLContextSymbols.h b/gfx/gl/GLContextSymbols.h
index d02377f2e64f..452b63e4ab79 100644
--- a/gfx/gl/GLContextSymbols.h
+++ b/gfx/gl/GLContextSymbols.h
@@ -487,7 +487,7 @@ struct GLContextSymbols
 
     typedef void (GLAPIENTRY * PFNGLGENTRANSFORMFEEDBACKSPROC) (GLsizei n, GLuint* ids);
     PFNGLGENTRANSFORMFEEDBACKSPROC fGenTransformFeedbacks;
-    typedef void (GLAPIENTRY * PFNGLDELETETRANSFORMFEEDBACKSPROC) (GLsizei n, GLuint* ids);
+    typedef void (GLAPIENTRY * PFNGLDELETETRANSFORMFEEDBACKSPROC) (GLsizei n, const GLuint* ids);
     PFNGLDELETETRANSFORMFEEDBACKSPROC fDeleteTransformFeedbacks;
     typedef realGLboolean (GLAPIENTRY * PFNGLISTRANSFORMFEEDBACKPROC) (GLuint id);
     PFNGLISTRANSFORMFEEDBACKPROC fIsTransformFeedback;