Enable browser plugin compositing by default, but add a flag to disable it.

content/browser/renderer_host/render_widget_host_view_guest.cc

Index: content/browser/renderer_host/render_widget_host_view_guest.cc
diff --git a/content/browser/renderer_host/render_widget_host_view_guest.cc b/content/browser/renderer_host/render_widget_host_view_guest.cc
index dc3f258007abce26656fd92d07a12a35c3ed5c7c..0bf9d3059a0b4e8106b398f4756f27c10d985669 100644
--- a/content/browser/renderer_host/render_widget_host_view_guest.cc
+++ b/content/browser/renderer_host/render_widget_host_view_guest.cc
@@ -28,9 +28,6 @@ RenderWidgetHostViewGuest::RenderWidgetHostViewGuest(
       is_hidden_(false),
       platform_view_(static_cast<RenderWidgetHostViewPort*>(platform_view)) {
   host_->SetView(this);
-
-  enable_compositing_ = CommandLine::ForCurrentProcess()->HasSwitch(
-      switches::kEnableBrowserPluginCompositing);
 }
 
 RenderWidgetHostViewGuest::~RenderWidgetHostViewGuest() {
@@ -103,34 +100,22 @@ void RenderWidgetHostViewGuest::SetTooltipText(const string16& tooltip_text) {
 void RenderWidgetHostViewGuest::AcceleratedSurfaceBuffersSwapped(
     const GpuHostMsg_AcceleratedSurfaceBuffersSwapped_Params& params,
     int gpu_host_id) {
-  DCHECK(enable_compositing_);
   // If accelerated surface buffers are getting swapped then we're not using
   // the software path.
   guest_->clear_damage_buffer();
-  if (enable_compositing_) {
-    guest_->SendMessageToEmbedder(
-        new BrowserPluginMsg_BuffersSwapped(
-            guest_->instance_id(),
-            params.size,
-            params.mailbox_name,
-            params.route_id,
-            gpu_host_id));
-  }
+  guest_->SendMessageToEmbedder(
+      new BrowserPluginMsg_BuffersSwapped(
+          guest_->instance_id(),
+          params.size,
+          params.mailbox_name,
+          params.route_id,
+          gpu_host_id));
 }
 
 void RenderWidgetHostViewGuest::AcceleratedSurfacePostSubBuffer(
     const GpuHostMsg_AcceleratedSurfacePostSubBuffer_Params& params,
     int gpu_host_id) {
-  DCHECK(enable_compositing_);
-  if (enable_compositing_) {

[Fady Samuel, 2013/03/07 15:21:44]

This is no longer necessary?

[alexst (slow to review), 2013/03/07 15:30:00]

I was working off the mistaken assumption that the whole buffer was there, and
just the damage rect was different. Right now, this won't work, so I am removing
it until we can find a fix.

-    guest_->SendMessageToEmbedder(
-        new BrowserPluginMsg_BuffersSwapped(
-            guest_->instance_id(),
-            params.surface_size,
-            params.mailbox_name,
-            params.route_id,
-            gpu_host_id));
-  }
+  NOTREACHED();
 }
 
 void RenderWidgetHostViewGuest::SetBounds(const gfx::Rect& rect) {
@@ -187,11 +172,7 @@ bool RenderWidgetHostViewGuest::HasFocus() const {
 }
 
 bool RenderWidgetHostViewGuest::IsSurfaceAvailableForCopy() const {
-  DCHECK(enable_compositing_);
-  if (enable_compositing_)
-    return true;
-  else
-    return platform_view_->IsSurfaceAvailableForCopy();
+  return true;

[Fady Samuel, 2013/03/07 15:21:44]

Hmm, so this changes the behavior with both compositing enabled and
disabled...presumably this simply isn't called if compositing is disabled?

[alexst (slow to review), 2013/03/07 15:30:00]

This shouldn't be called at all because I think it deals with the packing store.
In fact, I think this should be false.

[Fady Samuel, 2013/03/07 15:32:20]

If you're confident something shouldn't be called perhaps add a NOTREACHED() so
we catch it if things regress or there's a bug?

 }
 
 void RenderWidgetHostViewGuest::UpdateCursor(const WebCursor& cursor) {
@@ -265,11 +246,7 @@ void RenderWidgetHostViewGuest::AcceleratedSurfaceRelease() {
 
 bool RenderWidgetHostViewGuest::HasAcceleratedSurface(
       const gfx::Size& desired_size) {
-  DCHECK(enable_compositing_);
-  if (enable_compositing_)
-    return false;
-  else
-    return platform_view_->HasAcceleratedSurface(desired_size);

[Fady Samuel, 2013/03/07 15:21:44]

ditto.

[alexst (slow to review), 2013/03/07 15:30:00]

Shouldn't be called.

+  return false;
 }
 
 void RenderWidgetHostViewGuest::SetBackground(const SkBitmap& background) {