ppapi: Send sync point whenever the pepper texture changes.

content/renderer/pepper/ppb_graphics_3d_impl.cc

Index: content/renderer/pepper/ppb_graphics_3d_impl.cc
diff --git a/content/renderer/pepper/ppb_graphics_3d_impl.cc b/content/renderer/pepper/ppb_graphics_3d_impl.cc
index f143968c34d229f765915e5110f7ab80b6c3b188..519f9eb69a2e23b831c201b918918f37ec29d9e1 100644
--- a/content/renderer/pepper/ppb_graphics_3d_impl.cc
+++ b/content/renderer/pepper/ppb_graphics_3d_impl.cc
@@ -185,6 +185,10 @@ int32 PPB_Graphics3D_Impl::DoSwapBuffers() {
   if (gles2_impl())
     gles2_impl()->SwapBuffers();
 
+  // Since the backing texture has been updated, a new sync point should be
+  // inserted.
+  platform_context_->InsertSyncPointForBackingMailbox();
+
   if (bound_to_instance_) {
     // If we are bound to the instance, we need to ask the compositor
     // to commit our backing texture so that the graphics appears on the page.