Allow eviction of ImageBitmaps that are created from ImageElements.

Source/core/html/canvas/CanvasRenderingContext2D.cpp

Index: Source/core/html/canvas/CanvasRenderingContext2D.cpp
diff --git a/Source/core/html/canvas/CanvasRenderingContext2D.cpp b/Source/core/html/canvas/CanvasRenderingContext2D.cpp
index b2701331d1dffccff104b5be49378965be011792..0860353c00f7c8b83d7def99eb77290194cefad3 100644
--- a/Source/core/html/canvas/CanvasRenderingContext2D.cpp
+++ b/Source/core/html/canvas/CanvasRenderingContext2D.cpp
@@ -1275,9 +1275,9 @@ void CanvasRenderingContext2D::drawImage(ImageBitmap* bitmap,
     if (!imageRect.contains(normalizedSrcRect))
         return;
 
-    Image* imageForRendering = bitmap->bitmapImage();
+    RefPtr<Image> imageForRendering = bitmap->bitmapImage();
 
-    drawImageInternal(imageForRendering, normalizedSrcRect, actualDstRect, state().m_globalComposite, state().m_globalBlend);
+    drawImageInternal(imageForRendering.get(), normalizedSrcRect, actualDstRect, state().m_globalComposite, state().m_globalBlend);
 }
 
 void CanvasRenderingContext2D::drawImage(HTMLImageElement* image, float x, float y, ExceptionCode& ec)