diff --git a/include/gpu/GrConfig.h b/include/gpu/GrConfig.h
index 94c65d84a..95e518ab7 100644
--- a/include/gpu/GrConfig.h
+++ b/include/gpu/GrConfig.h
@@ -280,10 +280,13 @@ typedef unsigned __int64 uint64_t;
 #define GrAlwaysAssert(COND) GR_ALWAYSASSERT(COND)
 
 /**
- * Crash from unrecoverable condition, optionally with a message.
+ * Crash from unrecoverable condition, optionally with a message. The debug variants only
+ * crash in a debug build. The message versions print the message regardless of release vs debug.
  */
 inline void GrCrash() { GrAlwaysAssert(false); }
 inline void GrCrash(const char* msg) { GrPrintf(msg); GrAlwaysAssert(false); }
+inline void GrDebugCrash() { GrAssert(false); }
+inline void GrDebugCrash(const char* msg) { GrPrintf(msg); GrAssert(false); }
 
 /**
  *  GR_DEBUGCODE compiles the code X in debug builds only
diff --git a/include/gpu/GrEffect.h b/include/gpu/GrEffect.h
index 4cef4308e..20dc5dadc 100644
--- a/include/gpu/GrEffect.h
+++ b/include/gpu/GrEffect.h
@@ -153,7 +153,10 @@ public:
     GrTexture* texture(int index) const { return this->textureAccess(index).getTexture(); }
 
     /** Will this effect read the destination pixel value? */
-    bool willReadDst() const { return fWillReadDst; }
+    bool willReadDstColor() const { return fWillReadDstColor; }
+
+    /** Will this effect read the fragment position? */
+    bool willReadFragmentPosition() const { return fWillReadFragmentPosition; }
 
     int numVertexAttribs() const { return fVertexAttribTypes.count(); }
 
@@ -213,7 +216,7 @@ protected:
      */
     void addVertexAttrib(GrSLType type);
 
-    GrEffect() : fWillReadDst(false), fEffectRef(NULL) {}
+    GrEffect() : fWillReadDstColor(false), fWillReadFragmentPosition(false), fEffectRef(NULL) {}
 
     /** This should be called by GrEffect subclass factories. See the comment on AutoEffectUnref for
         an example factory function. */
@@ -269,7 +272,14 @@ protected:
      * from its constructor. Otherwise, when its generated backend-specific effect class attempts
      * to generate code that reads the destination pixel it will fail.
      */
-    void setWillReadDst() { fWillReadDst = true; }
+    void setWillReadDstColor() { fWillReadDstColor = true; }
+
+    /**
+     * If the effect will generate a backend-specific effect that will read the fragment position
+     * in the FS then it must call this method from its constructor. Otherwise, the request to
+     * access the fragment position will be denied.
+     */
+    void setWillReadFragmentPosition() { fWillReadFragmentPosition = true; }
 
 private:
     bool isEqual(const GrEffect& other) const {
@@ -302,7 +312,8 @@ private:
 
     SkSTArray<4, const GrTextureAccess*, true>   fTextureAccesses;
     SkSTArray<kMaxVertexAttribs, GrSLType, true> fVertexAttribTypes;
-    bool                                         fWillReadDst;
+    bool                                         fWillReadDstColor;
+    bool                                         fWillReadFragmentPosition;
     GrEffectRef*                                 fEffectRef;
 
     typedef GrRefCnt INHERITED;
diff --git a/src/core/SkXfermode.cpp b/src/core/SkXfermode.cpp
index eb03ef958..789606148 100644
--- a/src/core/SkXfermode.cpp
+++ b/src/core/SkXfermode.cpp
@@ -1358,7 +1358,7 @@ public:
     GR_DECLARE_EFFECT_TEST;
 
 private:
-    XferEffect(SkXfermode::Mode mode) : fMode(mode) { this->setWillReadDst(); }
+    XferEffect(SkXfermode::Mode mode) : fMode(mode) { this->setWillReadDstColor(); }
     virtual bool onIsEqual(const GrEffect& other) const SK_OVERRIDE { return true; }
 
     SkXfermode::Mode fMode;
diff --git a/src/effects/SkLightingImageFilter.cpp b/src/effects/SkLightingImageFilter.cpp
index bb2927bbf..c86bf6b62 100644
--- a/src/effects/SkLightingImageFilter.cpp
+++ b/src/effects/SkLightingImageFilter.cpp
@@ -447,6 +447,7 @@ public:
     virtual ~GrGLDistantLight() {}
     virtual void setData(const GrGLUniformManager&, const SkLight* light) const SK_OVERRIDE;
     virtual void emitSurfaceToLight(GrGLShaderBuilder*, const char* z) SK_OVERRIDE;
+
 private:
     typedef GrGLLight INHERITED;
     UniformHandle fDirectionUni;
@@ -459,6 +460,7 @@ public:
     virtual ~GrGLPointLight() {}
     virtual void setData(const GrGLUniformManager&, const SkLight* light) const SK_OVERRIDE;
     virtual void emitSurfaceToLight(GrGLShaderBuilder*, const char* z) SK_OVERRIDE;
+
 private:
     typedef GrGLLight INHERITED;
     SkPoint3 fLocation;
@@ -473,6 +475,7 @@ public:
     virtual void setData(const GrGLUniformManager&, const SkLight* light) const SK_OVERRIDE;
     virtual void emitSurfaceToLight(GrGLShaderBuilder*, const char* z) SK_OVERRIDE;
     virtual void emitLightColor(GrGLShaderBuilder*, const char *surfaceToLight) SK_OVERRIDE;
+
 private:
     typedef GrGLLight INHERITED;
 
@@ -509,6 +512,8 @@ public:
     virtual bool isEqual(const SkLight& other) const {
         return fColor == other.fColor;
     }
+    // Called to know whether the generated GrGLLight will require access to the fragment position.
+    virtual bool requiresFragmentPosition() const = 0;
 
 protected:
     SkLight(SkColor color)
@@ -553,6 +558,8 @@ public:
         return NULL;
 #endif
     }
+    virtual bool requiresFragmentPosition() const SK_OVERRIDE { return false; }
+
     virtual bool isEqual(const SkLight& other) const SK_OVERRIDE {
         if (other.type() != kDistant_LightType) {
             return false;
@@ -604,6 +611,7 @@ public:
         return NULL;
 #endif
     }
+    virtual bool requiresFragmentPosition() const SK_OVERRIDE { return true; }
     virtual bool isEqual(const SkLight& other) const SK_OVERRIDE {
         if (other.type() != kPoint_LightType) {
             return false;
@@ -674,6 +682,7 @@ public:
         return NULL;
 #endif
     }
+    virtual bool requiresFragmentPosition() const SK_OVERRIDE { return true; }
     virtual LightType type() const { return kSpot_LightType; }
     const SkPoint3& location() const { return fLocation; }
     const SkPoint3& target() const { return fTarget; }
@@ -1044,6 +1053,9 @@ GrLightingEffect::GrLightingEffect(GrTexture* texture, const SkLight* light, SkS
     , fLight(light)
     , fSurfaceScale(surfaceScale) {
     fLight->ref();
+    if (light->requiresFragmentPosition()) {
+        this->setWillReadFragmentPosition();
+    }
 }
 
 GrLightingEffect::~GrLightingEffect() {
diff --git a/src/gpu/GrAAHairLinePathRenderer.cpp b/src/gpu/GrAAHairLinePathRenderer.cpp
index a857dc4e9..4b10cea19 100644
--- a/src/gpu/GrAAHairLinePathRenderer.cpp
+++ b/src/gpu/GrAAHairLinePathRenderer.cpp
@@ -666,6 +666,7 @@ public:
 private:
     HairLineEdgeEffect() {
         this->addVertexAttrib(kVec4f_GrSLType);
+        this->setWillReadFragmentPosition();
     }
 
     virtual bool onIsEqual(const GrEffect& other) const SK_OVERRIDE {
diff --git a/src/gpu/GrAARectRenderer.cpp b/src/gpu/GrAARectRenderer.cpp
index 28dae2420..0b593b9a5 100644
--- a/src/gpu/GrAARectRenderer.cpp
+++ b/src/gpu/GrAARectRenderer.cpp
@@ -220,6 +220,7 @@ private:
     GrRectEffect() : GrEffect() {
         this->addVertexAttrib(kVec4f_GrSLType);
         this->addVertexAttrib(kVec2f_GrSLType);
+        this->setWillReadFragmentPosition();
     }
 
     virtual bool onIsEqual(const GrEffect&) const SK_OVERRIDE { return true; }
diff --git a/src/gpu/GrDrawState.h b/src/gpu/GrDrawState.h
index e34e4ab0e..91a8723e5 100644
--- a/src/gpu/GrDrawState.h
+++ b/src/gpu/GrDrawState.h
@@ -453,7 +453,7 @@ public:
      */
     bool willEffectReadDst() const {
         for (int s = 0; s < kNumStages; ++s) {
-            if (this->isStageEnabled(s) && (*this->getStage(s).getEffect())->willReadDst()) {
+            if (this->isStageEnabled(s) && (*this->getStage(s).getEffect())->willReadDstColor()) {
                 return true;
             }
         }
diff --git a/src/gpu/gl/GrGLProgramDesc.cpp b/src/gpu/gl/GrGLProgramDesc.cpp
index 1ae6aa69f..a1cd85e9f 100644
--- a/src/gpu/gl/GrGLProgramDesc.cpp
+++ b/src/gpu/gl/GrGLProgramDesc.cpp
@@ -87,7 +87,7 @@ void GrGLProgramDesc::Build(const GrDrawState& drawState,
             const GrBackendEffectFactory& factory = effect->getFactory();
             GrDrawEffect drawEffect(drawState.getStage(s), requiresLocalCoordAttrib);
             desc->fEffectKeys[s] = factory.glEffectKey(drawEffect, gpu->glCaps());
-            if (effect->willReadDst()) {
+            if (effect->willReadDstColor()) {
                 readsDst = true;
             }
         } else {
diff --git a/src/gpu/gl/GrGLShaderBuilder.cpp b/src/gpu/gl/GrGLShaderBuilder.cpp
index c1732b20e..98d7e4c97 100644
--- a/src/gpu/gl/GrGLShaderBuilder.cpp
+++ b/src/gpu/gl/GrGLShaderBuilder.cpp
@@ -230,6 +230,14 @@ void GrGLShaderBuilder::nameVariable(SkString* out, char prefix, const char* nam
 }
 
 const char* GrGLShaderBuilder::dstColor() {
+    if (fCodeStage.inStageCode()) {
+        const GrEffectRef& effect = *fCodeStage.effectStage()->getEffect();
+        if (!effect->willReadDstColor()) {
+            GrDebugCrash("GrGLEffect asked for dst color but its generating GrEffect "
+                         "did not request access.");
+            return "";
+        }
+    }
     static const char kFBFetchColorName[] = "gl_LastFragData[0]";
     GrGLCaps::FBFetchType fetchType = fCtxInfo.caps()->fbFetchType();
     if (GrGLCaps::kEXT_FBFetchType == fetchType) {
@@ -241,7 +249,7 @@ const char* GrGLShaderBuilder::dstColor() {
     } else if (fDstCopySampler.isInitialized()) {
         return kDstCopyColorName;
     } else {
-        return NULL;
+        return "";
     }
 }
 
@@ -457,6 +465,14 @@ void GrGLShaderBuilder::addVarying(GrSLType type,
 }
 
 const char* GrGLShaderBuilder::fragmentPosition() {
+    if (fCodeStage.inStageCode()) {
+        const GrEffectRef& effect = *fCodeStage.effectStage()->getEffect();
+        if (!effect->willReadFragmentPosition()) {
+            GrDebugCrash("GrGLEffect asked for frag position but its generating GrEffect "
+                         "did not request access.");
+            return "";
+        }
+    }
 #if 1
     if (fCtxInfo.caps()->fragCoordConventionsSupport()) {
         if (!fSetupFragPosition) {
diff --git a/tests/GLProgramsTest.cpp b/tests/GLProgramsTest.cpp
index 95187a6e3..d996cd740 100644
--- a/tests/GLProgramsTest.cpp
+++ b/tests/GLProgramsTest.cpp
@@ -63,7 +63,7 @@ void GrGLProgramDesc::setRandom(SkMWCRandom* random,
             const GrBackendEffectFactory& factory = (*stages[s]->getEffect())->getFactory();
             GrDrawEffect drawEffect(*stages[s], useLocalCoords);
             fEffectKeys[s] = factory.glEffectKey(drawEffect, gpu->glCaps());
-            if ((*stages[s]->getEffect())->willReadDst()) {
+            if ((*stages[s]->getEffect())->willReadDstColor()) {
                 dstRead = true;
             }
         }