Add decode() functionality to image elements.

third_party/WebKit/Source/web/WebViewImpl.h

 /*
  * Copyright (C) 2010 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 493 matching lines @@
   // Returns the currently active WebInputMethodController which is the one
   // corresponding to the focused frame. It will return nullptr if there is no
   // focused frame, or if the there is one but it belongs to a different local
   // root.
   WebInputMethodControllerImpl* GetActiveWebInputMethodController() const;
 
   void SetLastHiddenPagePopup(WebPagePopupImpl* page_popup) override {
     last_hidden_page_popup_ = page_popup;
   }
 
+  void RequestDecode(
+      sk_sp<SkImage>,
+      std::unique_ptr<WTF::Function<void(bool)>> callback) override;
+
  private:
   void SetPageScaleFactorAndLocation(float, const FloatPoint&);
   void PropagateZoomFactorToLocalFrameRoots(Frame*, float);
 
   void ScrollAndRescaleViewports(float scale_factor,
                                  const IntPoint& main_frame_origin,
                                  const FloatPoint& visual_viewport_origin);
 
   float MaximumLegiblePageScale() const;
   void RefreshPageScaleFactorAfterLayout();
@@ skipping 223 matching lines @@
   Persistent<ResizeViewportAnchor> resize_viewport_anchor_;
 };
 
 // We have no ways to check if the specified WebView is an instance of
 // WebViewImpl because WebViewImpl is the only implementation of WebView.
 DEFINE_TYPE_CASTS(WebViewImpl, WebView, webView, true, true);
 
 }  // namespace blink
 
 #endif