Allow ImageBitmaps derived from HTMLImageElements to be evicted from RAM.

Source/core/page/ImageBitmap.h

Index: Source/core/page/ImageBitmap.h
diff --git a/Source/core/page/ImageBitmap.h b/Source/core/page/ImageBitmap.h
index 102fa62542e219b514d12426121c2d17085a8e52..4edd4cd738d122c989d7a9ee3c750a4b2d4ae76d 100644
--- a/Source/core/page/ImageBitmap.h
+++ b/Source/core/page/ImageBitmap.h
@@ -32,6 +32,7 @@ public:
     PassRefPtr<HTMLImageElement> imageElement() const { return m_imageElement; }
 
     IntRect bitmapRect() const { return m_bitmapRect; }
+    IntPoint bitmapOffset() const { return m_bitmapOffset; }
 
     int width() const { return m_cropRect.width(); }
     int height() const { return m_cropRect.height(); }
@@ -57,6 +58,7 @@ private:
     OwnPtr<ImageBuffer> m_buffer;
 
     IntRect m_bitmapRect; // The rect where the underlying Image should be placed in reference to the ImageBitmap.
+    IntPoint m_bitmapOffset; // The offset by which the desired Image is stored internally.
     IntRect m_cropRect;
 };