Implementation of device metrics emulation in render view.

content/renderer/gpu/render_widget_compositor.cc

 // Copyright (c) 2013 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/renderer/gpu/render_widget_compositor.h"
 
 #include <limits>
 #include <string>
 
 #include "base/command_line.h"
@@ skipping 278 matching lines @@
   if (!compositor->initialize(settings))
     return scoped_ptr<RenderWidgetCompositor>();
 
   return compositor.Pass();
 }
 
 RenderWidgetCompositor::RenderWidgetCompositor(RenderWidget* widget,
                                                bool threaded)
     : threaded_(threaded),
       suppress_schedule_composite_(false),
-      widget_(widget) {
+      widget_(widget),
+      saved_device_scale_factor_(0.f) {
 }
 
 RenderWidgetCompositor::~RenderWidgetCompositor() {}
 
 const base::WeakPtr<cc::InputHandler>&
 RenderWidgetCompositor::GetInputHandler() {
   return layer_tree_host_->GetInputHandler();
 }
 
 void RenderWidgetCompositor::SetSuppressScheduleComposite(bool suppress) {
@@ skipping 97 matching lines @@
 WebSize RenderWidgetCompositor::deviceViewportSize() const {
   return layer_tree_host_->device_viewport_size();
 }
 
 WebFloatPoint RenderWidgetCompositor::adjustEventPointForPinchZoom(
     const WebFloatPoint& point) const {
   return point;
 }
 
 void RenderWidgetCompositor::setDeviceScaleFactor(float device_scale) {
-  layer_tree_host_->SetDeviceScaleFactor(device_scale);
+  if (saved_device_scale_factor_)
+    saved_device_scale_factor_ = device_scale;
+  else
+    layer_tree_host_->SetDeviceScaleFactor(device_scale);
+}
+
+void RenderWidgetCompositor::OverrideDeviceScaleFactor(float device_scale) {
+  if (device_scale) {
+    saved_device_scale_factor_ = deviceScaleFactor();
+    layer_tree_host_->SetDeviceScaleFactor(device_scale);
+  } else {
+    layer_tree_host_->SetDeviceScaleFactor(saved_device_scale_factor_);
+    saved_device_scale_factor_ = 0.f;
+  }
 }
 
 float RenderWidgetCompositor::deviceScaleFactor() const {
   return layer_tree_host_->device_scale_factor();
 }
 
 void RenderWidgetCompositor::setBackgroundColor(WebKit::WebColor color) {
   layer_tree_host_->set_background_color(color);
 }
 
@@ skipping 155 matching lines @@
   return RenderThreadImpl::current()->OffscreenContextProviderForMainThread();
 }
 
 scoped_refptr<cc::ContextProvider>
 RenderWidgetCompositor::OffscreenContextProviderForCompositorThread() {
   return RenderThreadImpl::current()->
       OffscreenContextProviderForCompositorThread();
 }
 
 }  // namespace content