Avoid rendering using GL in case damage rect is composited by overlay

cc/output/direct_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/direct_renderer.h"
 
 #include <utility>
 #include <vector>
 
 #include "base/containers/hash_tables.h"
@@ skipping 221 matching lines @@
     output_surface_plane.quad_rect_in_target_space =
         root_render_pass->output_rect;
     output_surface_plane.use_output_surface_for_resource = true;
     output_surface_plane.overlay_handled = true;
     frame.overlay_list.push_back(output_surface_plane);
   }
 
   // If we have any copy requests, we can't remove any quads for overlays,
   // otherwise the framebuffer will be missing the overlay contents.
   if (root_render_pass->copy_requests.empty()) {
+    bool needs_rendering = !frame.root_damage_rect.IsEmpty();
     overlay_processor_->ProcessForOverlays(
         resource_provider_, render_passes_in_draw_order, &frame.overlay_list);
+
+    // No need to render in case the damage rect is completely composited using
+    // overlays.
+    if (needs_rendering && frame.root_damage_rect.IsEmpty()) {

[piman, 2015/10/26 17:53:40]

Why the test for needs_rendering here?
Why would want to draw using GL instead if the root damage was empty before
ProcessForOverlays?

[kalyank, 2015/10/27 06:09:33]

Ya this wasn't needed, Fixed it. Added checks to make sure we don't have copy
requests for any of the RenderPass and damage rect is empty.

+      BindFramebufferToOutputSurface(&frame);
+      FinishDrawingFrame(&frame);
+      render_passes_in_draw_order->clear();
+      return;
+    }
   }
 
   for (size_t i = 0; i < render_passes_in_draw_order->size(); ++i) {
     RenderPass* pass = render_passes_in_draw_order->at(i);
     DrawRenderPass(&frame, pass);
 
     for (ScopedPtrVector<CopyOutputRequest>::iterator it =
              pass->copy_requests.begin();
          it != pass->copy_requests.end();
          ++it) {
@@ skipping 281 matching lines @@
   ScopedResource* texture = render_pass_textures_.get(id);
   return texture && texture->id();
 }
 
 // static
 gfx::Size DirectRenderer::RenderPassTextureSize(const RenderPass* render_pass) {
   return render_pass->output_rect.size();
 }
 
 }  // namespace cc