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..94bcfcf1b8da693f6158ca45b81d726302c2a44b 100644
--- a/Source/core/html/canvas/CanvasRenderingContext2D.cpp
+++ b/Source/core/html/canvas/CanvasRenderingContext2D.cpp
@@ -1260,7 +1260,6 @@ void CanvasRenderingContext2D::drawImage(ImageBitmap* bitmap,
         return;
 
     ASSERT(bitmap->height() && bitmap->width());
-
     FloatRect normalizedSrcRect = normalizeRect(srcRect);
     FloatRect normalizedDstRect = normalizeRect(dstRect);
     FloatRect actualDstRect(FloatPoint(bitmap->bitmapOffset()), bitmap->bitmapSize());
@@ -1274,10 +1273,9 @@ void CanvasRenderingContext2D::drawImage(ImageBitmap* bitmap,
     }
     if (!imageRect.contains(normalizedSrcRect))
         return;
+    RefPtr<Image> imageForRendering = bitmap->bitmapImage();
 
-    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)