Bug 1341521 - Remove the retaining buffer machanism when setting the same canvas dimension. r=nical

--HG--
extra : rebase_source : 519ae1558bb0a771474508ebfd1f44ea38262015

dom/canvas/CanvasRenderingContext2D.cpp

@@ -1906,11 +1906,7 @@ CanvasRenderingContext2D::GetHeight() const
 NS_IMETHODIMP
 CanvasRenderingContext2D::SetDimensions(int32_t aWidth, int32_t aHeight)
 {
-  bool retainBuffer = false;
-  if (aWidth == mWidth && aHeight == mHeight) {
-    retainBuffer = true;
-  }
-  ClearTarget(retainBuffer);
+  ClearTarget();
 
   // Zero sized surfaces can cause problems.
   mZero = false;
@@ -1929,23 +1925,10 @@ CanvasRenderingContext2D::SetDimensions(int32_t aWidth, int32_t aHeight)
 }
 
 void
-CanvasRenderingContext2D::ClearTarget(bool aRetainBuffer)
+CanvasRenderingContext2D::ClearTarget()
 {
-  RefPtr<PersistentBufferProvider> provider = mBufferProvider;
-  if (aRetainBuffer && provider) {
-    // We should reset the buffer data before reusing the buffer.
-    if (mTarget) {
-      mTarget->SetTransform(Matrix());
-    }
-    ClearRect(0, 0, mWidth, mHeight);
-  }
-
   Reset();
 
-  if (aRetainBuffer) {
-    mBufferProvider = provider;
-  }
-
   mResetLayer = true;
 
   SetInitialState();

dom/canvas/CanvasRenderingContext2D.h

@@ -682,7 +682,7 @@ protected:
   /**
    * Disposes an old target and prepares to lazily create a new target.
    */
-  void ClearTarget(bool aRetainBuffer = false);
+  void ClearTarget();
 
   /*
    * Returns the target to the buffer provider. i.e. this will queue a frame for