WebGL: paintRenderingResultsToImageData() must restore FBO.

Source/core/html/canvas/WebGLRenderingContextBase.cpp

 /*
  * Copyright (C) 2009 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 487 matching lines @@
 
     ~ScopedTexture2DRestorer()
     {
         m_context->restoreCurrentTexture2D();
     }
 
 private:
     RawPtrWillBeMember<WebGLRenderingContextBase> m_context;
 };
 
+class ScopedFramebufferRestorer {
+    STACK_ALLOCATED();
+public:
+    explicit ScopedFramebufferRestorer(WebGLRenderingContextBase* context)
+        : m_context(context)
+    {
+    }
+
+    ~ScopedFramebufferRestorer()
+    {
+        m_context->restoreCurrentFramebuffer();
+    }
+
+private:
+    RawPtrWillBeMember<WebGLRenderingContextBase> m_context;
+};
+
 class WebGLRenderingContextLostCallback final : public NoBaseWillBeGarbageCollectedFinalized<WebGLRenderingContextLostCallback>, public blink::WebGraphicsContext3D::WebGraphicsContextLostCallback {
     WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED;
 public:
     static PassOwnPtrWillBeRawPtr<WebGLRenderingContextLostCallback> create(WebGLRenderingContextBase* context)
     {
         return adoptPtrWillBeNoop(new WebGLRenderingContextLostCallback(context));
     }
 
     virtual ~WebGLRenderingContextLostCallback() { }
 
@@ skipping 387 matching lines @@
         return false;
 
     bool mustClearNow = clearIfComposited() != Skipped;
     if (!m_markedCanvasDirty && !mustClearNow)
         return false;
 
     canvas()->clearCopiedImage();
     m_markedCanvasDirty = false;
 
     ScopedTexture2DRestorer restorer(this);
+    ScopedFramebufferRestorer fboRestorer(this);
 
     drawingBuffer()->commit();
     if (!canvas()->buffer()->copyRenderingResultsFromDrawingBuffer(drawingBuffer(), sourceBuffer)) {
         canvas()->ensureUnacceleratedImageBuffer();
         if (canvas()->hasImageBuffer())
             drawingBuffer()->paintRenderingResultsToCanvas(canvas()->buffer());
     }
 
-    restoreCurrentFramebuffer();
     return true;
 }
 
 PassRefPtrWillBeRawPtr<ImageData> WebGLRenderingContextBase::paintRenderingResultsToImageData(SourceDrawingBuffer sourceBuffer)
 {
     if (isContextLost())
         return nullptr;
+    if (m_requestedAttributes.premultipliedAlpha())
+        return nullptr;
 
     clearIfComposited();
     drawingBuffer()->commit();
+    ScopedFramebufferRestorer restorer(this);
     int width, height;
     RefPtr<Uint8ClampedArray> imageDataPixels =
         drawingBuffer()->paintRenderingResultsToImageData(width, height, sourceBuffer);
     if (!imageDataPixels)
         return nullptr;
 
     return ImageData::create(IntSize(width, height), imageDataPixels);
 }
 
 void WebGLRenderingContextBase::reshape(int width, int height)
@@ skipping 5006 matching lines @@
     return m_sharedWebGraphicsContext3D ? m_sharedWebGraphicsContext3D->drawingBuffer() : 0;
 }
 #else
 DrawingBuffer* WebGLRenderingContextBase::drawingBuffer() const
 {
     return m_drawingBuffer.get();
 }
 #endif
 
 } // namespace blink