Fallback to RGBA_8888 if readback format is not supported

content/browser/renderer_host/render_widget_host_view_android.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CONTENT_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_VIEW_ANDROID_H_
 #define CONTENT_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_VIEW_ANDROID_H_
 
 #include <map>
 #include <queue>
 
@@ skipping 187 matching lines @@
   void OnDetachCompositor() override;
   void OnVSync(base::TimeTicks frame_time,
                base::TimeDelta vsync_period) override;
   void OnAnimate(base::TimeTicks begin_frame_time) override;
   void OnActivityPaused() override;
   void OnActivityResumed() override;
 
   // DelegatedFrameEvictor implementation
   void EvictDelegatedFrame() override;
 
-  SkColorType PreferredReadbackFormat() override;
-
   // StylusTextSelectorClient implementation.
   void OnStylusSelectBegin(float x0, float y0, float x1, float y1) override;
   void OnStylusSelectUpdate(float x, float y) override;
   void OnStylusSelectEnd() override;
   void OnStylusSelectTap(base::TimeTicks time, float x, float y) override;
 
   // ui::TouchSelectionControllerClient implementation.
   bool SupportsAnimation() const override;
   void SetNeedsAnimate() override;
   void MoveCaret(const gfx::PointF& position) override;
@@ skipping 212 matching lines @@
   gfx::Vector2dF last_scroll_offset_;
 
   base::WeakPtrFactory<RenderWidgetHostViewAndroid> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderWidgetHostViewAndroid);
 };
 
 } // namespace content
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_VIEW_ANDROID_H_