Browser side changes for software compositing

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 49 matching lines @@
   return make_scoped_ptr(
       new SoftwareRenderer(client, output_surface, resource_provider));
 }
 
 SoftwareRenderer::SoftwareRenderer(RendererClient* client,
                                    OutputSurface* output_surface,
                                    ResourceProvider* resource_provider)
   : DirectRenderer(client, resource_provider),
     visible_(true),
     is_scissor_enabled_(false),
+    is_viewport_changed_(true),
     output_surface_(output_surface),
     output_device_(output_surface->software_device()),
     current_canvas_(NULL) {
   resource_provider_->set_default_resource_type(ResourceProvider::Bitmap);
 
   capabilities_.max_texture_size = resource_provider_->max_texture_size();
   capabilities_.best_texture_format = resource_provider_->best_texture_format();
   capabilities_.using_set_visibility = true;
   // The updater can access bitmaps while the SoftwareRenderer is using them.
   capabilities_.allow_partial_texture_updates = true;
   capabilities_.using_partial_swap = true;
   if (Settings().compositor_frame_message && client_->HasImplThread())
     capabilities_.using_swap_complete_callback = true;
   compositor_frame_.software_frame_data.reset(new SoftwareFrameData());
-
-  ViewportChanged();
 }
 
 SoftwareRenderer::~SoftwareRenderer() {}
 
 const RendererCapabilities& SoftwareRenderer::Capabilities() const {
   return capabilities_;
 }
 
 void SoftwareRenderer::ViewportChanged() {
-  output_device_->Resize(ViewportSize());
+  is_viewport_changed_ = true;
 }
 
 void SoftwareRenderer::BeginDrawingFrame(DrawingFrame* frame) {
   TRACE_EVENT0("cc", "SoftwareRenderer::BeginDrawingFrame");
+  if (is_viewport_changed_) {
+    is_viewport_changed_ = false;
+    output_device_->Resize(ViewportSize());
+  }
   root_canvas_ = output_device_->BeginPaint(
       gfx::ToEnclosingRect(frame->root_damage_rect));
 }
 
 void SoftwareRenderer::FinishDrawingFrame(DrawingFrame* frame) {
   TRACE_EVENT0("cc", "SoftwareRenderer::FinishDrawingFrame");
   current_framebuffer_lock_.reset();
   current_canvas_ = NULL;
   root_canvas_ = NULL;
   if (Settings().compositor_frame_message) {
@@ skipping 305 matching lines @@
                              4 * rect.width());
 }
 
 void SoftwareRenderer::SetVisible(bool visible) {
   if (visible_ == visible)
     return;
   visible_ = visible;
 }
 
 }  // namespace cc