Relocate Image::transfer() to StaticBitmapImage

Not needed at the Image interface level.

R=junov@chromium.org

Review-Url: https://codereview.chromium.org/2590573002
Cr-Commit-Position: refs/heads/master@{#439848}

third_party/WebKit/Source/platform/graphics/Image.h

@@ -85,7 +85,6 @@ class PLATFORM_EXPORT Image : public ThreadSafeRefCounted<Image> {
   virtual bool currentFrameIsComplete() { return false; }
   virtual bool currentFrameIsLazyDecoded() { return false; }
   virtual bool isTextureBacked();
-  virtual void transfer() {}
 
   // Derived classes should override this if they can assure that the current
   // image frame contains only resources from its own security origin.

third_party/WebKit/Source/platform/graphics/StaticBitmapImage.h

@@ -40,6 +40,8 @@ class PLATFORM_EXPORT StaticBitmapImage : public Image {
   // sub-class
   virtual bool hasMailbox() { return false; }
 
+  virtual void transfer() {}
+
   // Methods overrided by AcceleratedStaticBitmapImage only
   virtual void copyToTexture(WebGraphicsContext3DProvider*,
                              GLuint,