cc: Allow output readback/copy requests to specify a sub-rect to copy.

cc/output/software_renderer.cc

 // Copyright 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 "cc/output/software_renderer.h"
 
 #include "base/debug/trace_event.h"
 #include "cc/base/math_util.h"
 #include "cc/output/compositor_frame.h"
 #include "cc/output/compositor_frame_ack.h"
@@ skipping 434 matching lines @@
   current_paint_.setColor(SK_ColorMAGENTA);
 #endif
   current_paint_.setAlpha(quad->opacity() * 255);
   current_canvas_->drawRect(gfx::RectFToSkRect(QuadVertexRect()),
                             current_paint_);
 }
 
 void SoftwareRenderer::CopyCurrentRenderPassToBitmap(
     DrawingFrame* frame,
     scoped_ptr<CopyOutputRequest> request) {
+  gfx::Rect copy_rect = frame->current_render_pass->output_rect;
+  if (request->has_area()) {
+    // Intersect with the request's area, positioned with its origin at the
+    // origin of the full copy_rect.
+    copy_rect.Intersect(request->area() - copy_rect.OffsetFromOrigin());
+  }
+  gfx::Rect window_copy_rect = MoveFromDrawToWindowSpace(copy_rect);
+
   scoped_ptr<SkBitmap> bitmap(new SkBitmap);
   bitmap->setConfig(SkBitmap::kARGB_8888_Config,
-                    current_viewport_rect_.width(),
-                    current_viewport_rect_.height());
+                    window_copy_rect.width(),
+                    window_copy_rect.height());
   current_canvas_->readPixels(
-      bitmap.get(), current_viewport_rect_.x(), current_viewport_rect_.y());
+      bitmap.get(), window_copy_rect.x(), window_copy_rect.y());
 
   request->SendBitmapResult(bitmap.Pass());
 }
 
 void SoftwareRenderer::GetFramebufferPixels(void* pixels, gfx::Rect rect) {
   TRACE_EVENT0("cc", "SoftwareRenderer::GetFramebufferPixels");
   SkBitmap subset_bitmap;
   rect += current_viewport_rect_.OffsetFromOrigin();
   output_device_->CopyToBitmap(rect, &subset_bitmap);
   subset_bitmap.copyPixelsTo(pixels,
                              4 * rect.width() * rect.height(),
                              4 * rect.width());
 }
 
 void SoftwareRenderer::SetVisible(bool visible) {
   if (visible_ == visible)
     return;
   visible_ = visible;
 }
 
 }  // namespace cc