Fix for 686083: Adds method to disable GL implementations

gfx/thebes/GLContextProviderCGL.mm

@@ -46,6 +46,7 @@
 #include "gfxPlatform.h"
 #include "gfxFailure.h"
 #include "prenv.h"
+#include "mozilla/Preferences.h"
 
 namespace mozilla {
 namespace gl {
@@ -559,6 +560,10 @@ GLContextProviderCGL::CreateOffscreen(const gfxIntSize& aSize,
 {
     nsRefPtr<GLContextCGL> glContext;
     
+    NS_ENSURE_TRUE(Preferences::GetRootBranch(), nsnull);
+    const bool preferFBOs = Preferences::GetBool("cgl.prefer-fbo", false);
+    if (!preferFBOs)
+    {
 	    glContext = CreateOffscreenPBufferContext(aSize, aFormat);
 	    if (glContext &&
 	        glContext->Init())
@@ -568,6 +573,7 @@ GLContextProviderCGL::CreateOffscreen(const gfxIntSize& aSize,
 
 	        return glContext.forget();
 	    }
+	}
 
     // try a FBO as second choice
     glContext = CreateOffscreenFBOContext(aSize, aFormat);

gfx/thebes/GLContextProviderWGL.cpp

@@ -48,6 +48,8 @@
 
 #include "prenv.h"
 
+#include "mozilla/Preferences.h"
+
 namespace mozilla {
 namespace gl {
 
@@ -616,7 +618,10 @@ GLContextProviderWGL::CreateOffscreen(const gfxIntSize& aSize,
 
     // Always try to create a pbuffer context first, because we
     // want the context isolation.
-    if (sWGLLibrary.fCreatePbuffer &&
+    NS_ENSURE_TRUE(Preferences::GetRootBranch(), nsnull);
+    const bool preferFBOs = Preferences::GetBool("wgl.prefer-fbo", false);
+    if (!preferFBOs &&
+        sWGLLibrary.fCreatePbuffer &&
         sWGLLibrary.fChoosePixelFormat)
     {
         glContext = CreatePBufferOffscreenContext(aSize, aFormat);