Add a command line flag (--enable-fixed-position-compositing) for enabling compositing

of fixed position elements.

BUG=None
TEST=Manual testing to verify the flag works.
Review URL: http://codereview.chromium.org/8404026

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@108166 0039d316-1c4b-4281-b951-d872f2087c98

chrome/browser/tab_contents/render_view_host_delegate_helper.cc

@@ -449,6 +449,8 @@ WebPreferences RenderViewHostDelegateHelper::GetWebkitPrefs(
         command_line.HasSwitch(switches::kEnableThreadedCompositing);
     web_prefs.force_compositing_mode =
         command_line.HasSwitch(switches::kForceCompositingMode);
+    web_prefs.fixed_position_compositing_enabled =
+        command_line.HasSwitch(switches::kEnableCompositingForFixedPosition);
     web_prefs.allow_webui_compositing =
         command_line.HasSwitch(switches::kAllowWebUICompositing);
     web_prefs.accelerated_2d_canvas_enabled =

content/common/view_messages.h

@@ -232,6 +232,7 @@ IPC_STRUCT_TRAITS_BEGIN(WebPreferences)
   IPC_STRUCT_TRAITS_MEMBER(force_compositing_mode)
   IPC_STRUCT_TRAITS_MEMBER(allow_webui_compositing)
   IPC_STRUCT_TRAITS_MEMBER(composite_to_texture_enabled)
+  IPC_STRUCT_TRAITS_MEMBER(fixed_position_compositing_enabled)
   IPC_STRUCT_TRAITS_MEMBER(accelerated_2d_canvas_enabled)
   IPC_STRUCT_TRAITS_MEMBER(accelerated_drawing_enabled)
   IPC_STRUCT_TRAITS_MEMBER(accelerated_plugins_enabled)

content/public/common/content_switches.cc

@@ -181,6 +181,10 @@ const char kEnableAccessibility[]           = "enable-accessibility";
 // Turns on extremely verbose logging of accessibility events.
 const char kEnableAccessibilityLogging[]    = "enable-accessibility-logging";
 
+// Enables the creation of compositing layers for fixed position elements.
+const char kEnableCompositingForFixedPosition[] =
+     "enable-fixed-position-compositing";
+
 // Enable DNS side checking of certificates. Still experimental, should only
 // be used by developers at the current time.
 const char kEnableDNSCertProvenanceChecking[] =

content/public/common/content_switches.h

@@ -67,6 +67,7 @@ extern const char kEnableAccelerated2dCanvas[];
 CONTENT_EXPORT extern const char kEnableAcceleratedDrawing[];
 extern const char kEnableAccessibility[];
 extern const char kEnableAccessibilityLogging[];
+CONTENT_EXPORT extern const char kEnableCompositingForFixedPosition[];
 CONTENT_EXPORT extern const char kEnableDNSCertProvenanceChecking[];
 CONTENT_EXPORT extern const char kEnableDeviceMotion[];
 CONTENT_EXPORT extern const char kDisableFullScreen[];

webkit/glue/webpreferences.cc

@@ -79,6 +79,7 @@ WebPreferences::WebPreferences()
       force_compositing_mode(false),
       allow_webui_compositing(false),
       composite_to_texture_enabled(false),
+      fixed_position_compositing_enabled(false),
       accelerated_layers_enabled(false),
       accelerated_video_enabled(false),
       accelerated_2d_canvas_enabled(false),
@@ -264,6 +265,11 @@ void WebPreferences::Apply(WebView* web_view) const {
   // Enable composite to offscreen texture if requested on the command line.
   settings->setCompositeToTextureEnabled(composite_to_texture_enabled);
 
+  // Enable compositing for fixed position elements if requested
+  // on the command line.
+  settings->setAcceleratedCompositingForFixedPositionEnabled(
+      fixed_position_compositing_enabled);
+
   // Enable gpu-accelerated 2d canvas if requested on the command line.
   settings->setAccelerated2dCanvasEnabled(accelerated_2d_canvas_enabled);
 

webkit/glue/webpreferences.h

@@ -93,6 +93,7 @@ struct WebPreferences {
   bool force_compositing_mode;
   bool allow_webui_compositing;
   bool composite_to_texture_enabled;
+  bool fixed_position_compositing_enabled;
   bool accelerated_layers_enabled;
   bool accelerated_video_enabled;
   bool accelerated_2d_canvas_enabled;