RenderWidget's scheduleComposite should return a bool. (true iff a prompt composite will come).

content/renderer/render_widget.cc

Index: content/renderer/render_widget.cc
diff --git a/content/renderer/render_widget.cc b/content/renderer/render_widget.cc
index e21aeda4b03bce52228e785255e7a77e5c2dc0b2..6ba68691fddcd60ddcb9b6ec5a502b686b4db9c0 100644
--- a/content/renderer/render_widget.cc
+++ b/content/renderer/render_widget.cc
@@ -1161,6 +1161,23 @@ void RenderWidget::didCompleteSwapBuffers() {
   next_paint_flags_ = 0;
 }
 
+#if defined(WEBWIDGETCLIENT_SCHEDULECOMPOSITE_RETURNS_BOOL)
+bool RenderWidget::scheduleComposite() {

[nduca, 2012/05/02 06:53:00]

Can you fix this with less code duplication? E.g.
#if returnsbool
#define sc_return_value bool
#else
#define sc_return_value void
#endif

then inside the function, #if sc_returns_bool
custom return
#endif

+  if (WebWidgetHandlesCompositorScheduling()) {
+    webwidget_->composite(false);
+    return true;
+  }
+
+  // TODO(nduca): replace with something a little less hacky.  The reason this
+  // hack is still used is because the Invalidate-DoDeferredUpdate loop
+  // contains a lot of host-renderer synchronization logic that is still
+  // important for the accelerated compositing case. The option of simply
+  // duplicating all that code is less desirable than "faking out" the
+  // invalidation path using a magical damage rect.
+  didInvalidateRect(WebRect(0, 0, 1, 1));
+  return !is_hidden_;

[nduca, 2012/05/02 06:53:00]

This feels fragile to me. You're assuming things here about didInvalidateRect.
It woul dbe better for didInvalidateRect to give the return value. Do this by
moving the body of didInval to a DoInvalidateRect function and then making
didInvalidateRect just call to Do?

+}
+#else
 void RenderWidget::scheduleComposite() {
   if (WebWidgetHandlesCompositorScheduling()) {
     webwidget_->composite(false);
@@ -1174,6 +1191,7 @@ void RenderWidget::scheduleComposite() {
     didInvalidateRect(WebRect(0, 0, 1, 1));
   }
 }
+#endif
 
 void RenderWidget::scheduleAnimation() {
   if (animation_update_pending_)