Adds scroll position/scale emulation to DevTools.

content/renderer/devtools/render_widget_screen_metrics_emulator.cc

 // Copyright 2016 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/devtools/render_widget_screen_metrics_emulator.h"
 
 #include "content/common/resize_params.h"
 #include "content/public/common/context_menu_params.h"
 #include "content/renderer/devtools/render_widget_screen_metrics_emulator_delegate.h"
 
@@ skipping 108 matching lines @@
   modified_emulation_params.scale = scale_;
   delegate_->SetScreenMetricsEmulationParameters(true,
                                                  modified_emulation_params);
 
   delegate_->SetScreenRects(applied_widget_rect_, window_screen_rect);
 
   modified_resize_params.physical_backing_size =
       gfx::ScaleToCeiledSize(original_resize_params_.new_size,
                              original_screen_info().deviceScaleFactor);
   modified_resize_params.new_size = applied_widget_rect_.size();
-  modified_resize_params.visible_viewport_size = applied_widget_rect_.size();
+
+  gfx::Size visible_viewport_size = applied_widget_rect_.size();
+  if (emulation_params_.visualViewportSize.width) {
+    visible_viewport_size.set_width(
+        emulation_params_.visualViewportSize.width);
+  }
+  if (emulation_params_.visualViewportSize.height) {
+    visible_viewport_size.set_height(
+        emulation_params_.visualViewportSize.height);
+  }
+  modified_resize_params.visible_viewport_size = visible_viewport_size;
+
   modified_resize_params.needs_resize_ack = false;
   delegate_->Resize(modified_resize_params);
 }
 
 void RenderWidgetScreenMetricsEmulator::OnResize(const ResizeParams& params) {
   original_resize_params_ = params;
   Apply();
 
   if (params.needs_resize_ack)
     delegate_->Redraw();
@@ skipping 28 matching lines @@
 
 gfx::Rect RenderWidgetScreenMetricsEmulator::AdjustValidationMessageAnchor(
     const gfx::Rect& anchor) {
   gfx::Rect scaled = gfx::ScaleToEnclosedRect(anchor, scale_);
   scaled.set_x(scaled.x() + offset_.x());
   scaled.set_y(scaled.y() + offset_.y());
   return scaled;
 }
 
 }  // namespace content