Revert of WebGL: Free temporary GPU resources held by inactive or hidden WebGL.

Source/platform/graphics/gpu/DrawingBuffer.h

Index: Source/platform/graphics/gpu/DrawingBuffer.h
diff --git a/Source/platform/graphics/gpu/DrawingBuffer.h b/Source/platform/graphics/gpu/DrawingBuffer.h
index 545918e95e4265cdca195252de0871abb62f12ba..4c457b7c7b747dc97b8763a629758a6bbe6de54f 100644
--- a/Source/platform/graphics/gpu/DrawingBuffer.h
+++ b/Source/platform/graphics/gpu/DrawingBuffer.h
@@ -142,7 +142,6 @@
     void markContentsChanged();
     void markLayerComposited();
     bool layerComposited() const;
-    void setIsHidden(bool);
 
     blink::WebLayer* platformLayer();
     void paintCompositedResultsToCanvas(ImageBuffer*);
@@ -179,7 +178,7 @@
     bool initialize(const IntSize&);
 
 private:
-    void mailboxReleasedWithoutRecycling(const blink::WebExternalTextureMailbox&);
+    void mailboxReleasedWhileDestructionInProgress(const blink::WebExternalTextureMailbox&);
 
     unsigned createColorTexture();
     // Create the depth/stencil and multisample buffers, if needed.
@@ -196,7 +195,6 @@
     PassRefPtr<MailboxInfo> recycledMailbox();
     PassRefPtr<MailboxInfo> createNewMailbox(const TextureInfo&);
     void deleteMailbox(const blink::WebExternalTextureMailbox&);
-    void freeRecycledMailboxes();
 
     // Updates the current size of the buffer, ensuring that s_currentResourceUsePixels is updated.
     void setSize(const IntSize& size);
@@ -281,7 +279,6 @@
     int m_sampleCount;
     int m_packAlignment;
     bool m_destructionInProgress;
-    bool m_isHidden;
 
     OwnPtr<blink::WebExternalTextureLayer> m_layer;