Support copying a partial rectangle region from the compositing surface on Mac.

content/browser/renderer_host/render_widget_host_view_mac.mm

 // 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.
 
 #include "content/browser/renderer_host/render_widget_host_view_mac.h"
 
 #include <QuartzCore/QuartzCore.h>
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
@@ skipping 804 matching lines @@
   float scale = ScaleFactor(cocoa_view_);
   return new BackingStoreMac(render_widget_host_, size, scale);
 }
 
 void RenderWidgetHostViewMac::CopyFromCompositingSurface(
     const gfx::Rect& src_subrect,
     const gfx::Size& dst_size,
     const base::Callback<void(bool)>& callback,
     skia::PlatformCanvas* output) {
   base::ScopedClosureRunner scoped_callback_runner(base::Bind(callback, false));
-  // TODO(mazda): Support copying a partial rectangle from the compositing
-  // surface with |src_subrect| (http://crbug.com/118571).
-  if (!src_subrect.IsEmpty()) {
-    NOTIMPLEMENTED();
-    return;
-  }
-
   if (!compositing_iosurface_.get() ||
       !compositing_iosurface_->HasIOSurface())
     return;
 
-  if (!output->initialize(dst_size.width(), dst_size.height(), true))
+  float scale = ScaleFactor(cocoa_view_);
+  gfx::Size dst_pixel_size = dst_size.Scale(scale);
+  if (!output->initialize(
+      dst_pixel_size.width(), dst_pixel_size.height(), true))
     return;
 
+  gfx::Rect src_pixel_subrect(src_subrect.origin().Scale(scale),
+                              src_subrect.size().Scale(scale));
   const bool result = compositing_iosurface_->CopyTo(
-      dst_size, output->getTopDevice()->accessBitmap(true).getPixels());
+      src_pixel_subrect,
+      dst_pixel_size,
+      output->getTopDevice()->accessBitmap(true).getPixels());
   scoped_callback_runner.Release();
   callback.Run(result);
 }
 
 // Sets whether or not to accept first responder status.
 void RenderWidgetHostViewMac::SetTakesFocusOnlyOnMouseDown(bool flag) {
   [cocoa_view_ setTakesFocusOnlyOnMouseDown:flag];
 }
 
 void RenderWidgetHostViewMac::ForwardMouseEvent(const WebMouseEvent& event) {
@@ skipping 2361 matching lines @@
   if (!string) return NO;
 
   // If the user is currently using an IME, confirm the IME input,
   // and then insert the text from the service, the same as TextEdit and Safari.
   [self confirmComposition];
   [self insertText:string];
   return YES;
 }
 
 @end