android: add Java-side support for browser compositor async readback

content/public/browser/android/compositor.h

Index: content/public/browser/android/compositor.h
diff --git a/content/public/browser/android/compositor.h b/content/public/browser/android/compositor.h
index 236a90dd00d4703b40142317be9787071963a9fb..2d8126b3dbb33eae2d31271d65f7c92b8d8e5da8 100644
--- a/content/public/browser/android/compositor.h
+++ b/content/public/browser/android/compositor.h
@@ -64,11 +64,6 @@ class CONTENT_EXPORT Compositor {
   // Tells the view tree to assume a transparent background when rendering.
   virtual void SetHasTransparentBackground(bool flag) = 0;
 
-  // Attempts to composite and read back the result into the provided buffer.
-  // The buffer must be at least window width * height * 4 (RGBA) bytes large.
-  // The buffer is not modified if false is returned.
-  virtual bool CompositeAndReadback(void *pixels, const gfx::Rect& rect) = 0;
-
   // Request layout and draw. You only need to call this if you need to trigger
   // Composite *without* having modified the layer tree.
   virtual void SetNeedsComposite() = 0;