Add flag to experiments to force high DPI mode.

content/renderer/render_view_impl.cc

 // Copyright (c) 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 "content/renderer/render_view_impl.h"
 
 #include <algorithm>
 #include <cmath>
 #include <string>
 #include <vector>
@@ skipping 2648 matching lines @@
     navigation_state->set_transferred_request_request_id(
         params.transferred_request_request_id);
   } else {
     navigation_state = NavigationState::CreateContentInitiated();
   }
   return navigation_state;
 }
 
 void RenderViewImpl::ProcessViewLayoutFlags(const CommandLine& command_line) {
   bool enable_viewport =
-      command_line.HasSwitch(switches::kEnableViewport);
+      command_line.HasSwitch(switches::kEnableViewport) ||
+      // Setting a default device scale factor forces enable_viewport on.
+      webkit_preferences_.default_device_scale_factor > 1;
   bool enable_fixed_layout =
       command_line.HasSwitch(switches::kEnableFixedLayout);
 
   webview()->enableFixedLayoutMode(enable_fixed_layout || enable_viewport);
   webview()->settings()->setFixedElementsLayoutRelativeToFrame(true);
 
   if (enable_viewport) {
     webview()->settings()->setViewportEnabled(true);
   } else if (enable_fixed_layout) {
     std::string str =
@@ skipping 2577 matching lines @@
 bool RenderViewImpl::WebWidgetHandlesCompositorScheduling() const {
   return !!RenderThreadImpl::current()->compositor_thread();
 }
 
 void RenderViewImpl::OnJavaBridgeInit() {
   DCHECK(!java_bridge_dispatcher_.get());
 #if defined(ENABLE_JAVA_BRIDGE)
   java_bridge_dispatcher_.reset(new JavaBridgeDispatcher(this));
 #endif
 }