Enable accelerated overflow scrolling for high dpi.

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 "base/auto_reset.h"
@@ skipping 575 matching lines @@
 
   if (command_line.HasSwitch(switches::kDisableCompositingForFixedPosition))
     return false;
 
   if (command_line.HasSwitch(switches::kEnableCompositingForFixedPosition))
     return true;
 
   return DeviceScaleEnsuresTextQuality(device_scale_factor);
 }
 
+static bool ShouldUseAcceleratedCompositingForOverflowScroll(
+    float device_scale_factor) {
+  const CommandLine& command_line = *CommandLine::ForCurrentProcess();
+
+  if (command_line.HasSwitch(switches::kEnableAcceleratedOverflowScroll))
+    return true;
+
+  return DeviceScaleEnsuresTextQuality(device_scale_factor);
+}
+
 static bool ShouldUseTransitionCompositing(float device_scale_factor) {
   const CommandLine& command_line = *CommandLine::ForCurrentProcess();
 
   if (command_line.HasSwitch(switches::kDisableCompositingForTransition))
     return false;
 
   if (command_line.HasSwitch(switches::kEnableCompositingForTransition))
     return true;
 
   // TODO(ajuma): Re-enable this by default for high-DPI once the problem
@@ skipping 269 matching lines @@
   if (opener_id_ == MSG_ROUTING_NONE) {
     did_show_ = true;
     CompleteInit();
   }
 
   g_view_map.Get().insert(std::make_pair(webview(), this));
   g_routing_id_view_map.Get().insert(std::make_pair(routing_id_, this));
   webview()->setDeviceScaleFactor(device_scale_factor_);
   webview()->settings()->setAcceleratedCompositingForFixedPositionEnabled(
       ShouldUseFixedPositionCompositing(device_scale_factor_));
+  webview()->settings()->setAcceleratedCompositingForOverflowScrollEnabled(
+      ShouldUseAcceleratedCompositingForOverflowScroll(device_scale_factor_));
   webview()->settings()->setAcceleratedCompositingForTransitionEnabled(
       ShouldUseTransitionCompositing(device_scale_factor_));
 
   webkit_glue::ApplyWebPreferences(webkit_preferences_, webview());
   webview()->initializeMainFrame(this);
 
   if (switches::IsTouchDragDropEnabled())
     webview()->settings()->setTouchDragDropEnabled(true);
 
   if (switches::IsTouchEditingEnabled())
@@ skipping 5318 matching lines @@
     RenderWidget::OnImeConfirmComposition(text, replacement_range);
   }
 }
 
 void RenderViewImpl::SetDeviceScaleFactor(float device_scale_factor) {
   RenderWidget::SetDeviceScaleFactor(device_scale_factor);
   if (webview()) {
     webview()->setDeviceScaleFactor(device_scale_factor);
     webview()->settings()->setAcceleratedCompositingForFixedPositionEnabled(
         ShouldUseFixedPositionCompositing(device_scale_factor_));
+  webview()->settings()->setAcceleratedCompositingForOverflowScrollEnabled(
+      ShouldUseAcceleratedCompositingForOverflowScroll(device_scale_factor_));
     webview()->settings()->setAcceleratedCompositingForTransitionEnabled(
         ShouldUseTransitionCompositing(device_scale_factor_));
   }
   if (auto_resize_mode_)
     AutoResizeCompositor();
 
   if (browser_plugin_manager_.get())
     browser_plugin_manager_->UpdateDeviceScaleFactor(device_scale_factor_);
 }
 
@@ skipping 532 matching lines @@
     WebURL url = icon_urls[i].iconURL();
     if (!url.isEmpty())
       urls.push_back(FaviconURL(url,
                                 ToFaviconType(icon_urls[i].iconType())));
   }
   SendUpdateFaviconURL(urls);
 }
 
 
 }  // namespace content