Fix high-DPI on Windows to make use of DIP scaling in WebKit.

content/browser/web_contents/web_contents_impl.cc

Index: content/browser/web_contents/web_contents_impl.cc
diff --git a/content/browser/web_contents/web_contents_impl.cc b/content/browser/web_contents/web_contents_impl.cc
index b7b43b4d1100903f4426ea07bec09ef70232ecff..3708c9eb8235f166fd83b5a7f8b272a6e4ad95e0 100644
--- a/content/browser/web_contents/web_contents_impl.cc
+++ b/content/browser/web_contents/web_contents_impl.cc
@@ -480,9 +480,13 @@ WebPreferences WebContentsImpl::GetWebkitPrefs(RenderViewHost* rvh,
   prefs.accelerated_compositing_enabled =
       GpuProcessHost::gpu_enabled() &&
       !command_line.HasSwitch(switches::kDisableAcceleratedCompositing);
+#if defined(OS_WIN) && defined(ENABLE_HIDPI)
+  prefs.force_compositing_mode = true;
+#else
   prefs.force_compositing_mode =
       command_line.HasSwitch(switches::kForceCompositingMode) &&
       !command_line.HasSwitch(switches::kDisableForceCompositingMode);
+#endif
   prefs.fixed_position_compositing_enabled =
       command_line.HasSwitch(switches::kEnableCompositingForFixedPosition);
   prefs.accelerated_2d_canvas_enabled =
@@ -605,6 +609,10 @@ WebPreferences WebContentsImpl::GetWebkitPrefs(RenderViewHost* rvh,
 
   prefs.is_online = !net::NetworkChangeNotifier::IsOffline();
 
+#if defined(OS_WIN) && defined(ENABLE_HIDPI)
+  prefs.accelerated_compositing_enabled = true;
+  prefs.accelerated_2d_canvas_enabled = true;
+#else
   // Force accelerated compositing and 2d canvas off for chrome:, about: and
   // chrome-devtools: pages (unless it's specifically allowed).
   if ((url.SchemeIs(chrome::kChromeDevToolsScheme) ||
@@ -615,7 +623,7 @@ WebPreferences WebContentsImpl::GetWebkitPrefs(RenderViewHost* rvh,
     prefs.accelerated_compositing_enabled = false;
     prefs.accelerated_2d_canvas_enabled = false;
   }
-
+#endif
   if (command_line.HasSwitch(switches::kDefaultTileWidth))
     prefs.default_tile_width =
         GetSwitchValueAsInt(command_line, switches::kDefaultTileWidth, 1);