Remove DocumentVisibilityObserver

sky/engine/core/html/HTMLCanvasElement.cpp

 /*
  * Copyright (C) 2004, 2006, 2007 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Alp Toker <alp@atoker.com>
  * Copyright (C) 2010 Torch Mobile (Beijing) Co. Ltd. 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.
@@ skipping 58 matching lines @@
 // in exchange for a smaller maximum canvas size.
 static const int MaxCanvasArea = 32768 * 8192; // Maximum canvas area in CSS pixels
 
 //In Skia, we will also limit width/height to 32767.
 static const int MaxSkiaDim = 32767; // Maximum width/height in CSS pixels.
 
 DEFINE_EMPTY_DESTRUCTOR_WILL_BE_REMOVED(CanvasObserver);
 
 inline HTMLCanvasElement::HTMLCanvasElement(Document& document)
     : HTMLElement(HTMLNames::canvasTag, document)
-    , DocumentVisibilityObserver(document)
     , m_size(DefaultWidth, DefaultHeight)
     , m_ignoreReset(false)
     , m_accelerationDisabled(false)
     , m_externallyAllocatedMemory(0)
     , m_didFailToCreateImageBuffer(false)
     , m_didClearImageBuffer(false)
 {
 }
 
 DEFINE_NODE_FACTORY(HTMLCanvasElement)
@@ skipping 555 matching lines @@
     }
     m_didClearImageBuffer = false;
 }
 
 AffineTransform HTMLCanvasElement::baseTransform() const
 {
     ASSERT(hasImageBuffer() && !m_didFailToCreateImageBuffer);
     return m_imageBuffer->baseTransform();
 }
 
-void HTMLCanvasElement::didChangeVisibilityState(PageVisibilityState visibility)
-{
-    if (!m_context)
-        return;
-    bool hidden = visibility != PageVisibilityStateVisible;
-    m_context->setIsHidden(hidden);
-    if (hidden) {
-        clearCopiedImage();
-        if (is3D()) {
-            discardImageBuffer();
-        }
-    }
-}
-
-void HTMLCanvasElement::didMoveToNewDocument(Document& oldDocument)
-{
-    setObservedDocument(document());
-    HTMLElement::didMoveToNewDocument(oldDocument);
-}
-
 PassRefPtr<Image> HTMLCanvasElement::getSourceImageForCanvas(SourceImageMode mode, SourceImageStatus* status) const
 {
     if (!width() || !height()) {
         *status = ZeroSizeCanvasSourceImageStatus;
         return nullptr;
     }
 
     if (!buffer()) {
         *status = InvalidSourceImageStatus;
         return nullptr;
@@ skipping 12 matching lines @@
     }
     return m_imageBuffer->copyImage(DontCopyBackingStore, Unscaled);
 }
 
 FloatSize HTMLCanvasElement::sourceSize() const
 {
     return FloatSize(width(), height());
 }
 
 }