Expose SignalSyncPoint through MGL api

mojo/gles2/mgl_impl.cc

Index: mojo/gles2/mgl_impl.cc
diff --git a/mojo/gles2/mgl_impl.cc b/mojo/gles2/mgl_impl.cc
index 95eb09388090723c6f8406c44f1d41e571786541..96861a5c9ff6cc0b1f2a21e152ddf659f9b14119 100644
--- a/mojo/gles2/mgl_impl.cc
+++ b/mojo/gles2/mgl_impl.cc
@@ -35,6 +35,13 @@ MGLContext MGLGetCurrentContext() {
   return gles2::ControlThunksImpl::Get()->GetCurrentContext();
 }
 
+void MGLSignalSyncPoint(uint32_t sync_point,
+                        MGLSignalSyncPointCallback callback,
+                        void* closure) {
+  gles2::ControlThunksImpl::Get()->SignalSyncPoint(sync_point, callback,
+                                                   closure);
+}
+
 void MGLResizeSurface(uint32_t width, uint32_t height) {
   return gles2::ControlThunksImpl::Get()->ResizeSurface(width, height);
 }