Expose SignalSyncPoint through MGL api

mojo/public/c/gpu/BUILD.gn

 # Copyright 2015 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("../../mojo_sdk.gni")
 
 config("gpu_configs") {
   include_dirs = [ "." ]
   defines = [ "GLES2_USE_MOJO" ]
 }
 
 group("gpu") {
   public_configs = [ ":gpu_configs" ]
 
   deps = [
     ":MGL",
+    ":MGL_signal_sync_point",
     ":GLES2",
     "../../platform/native:mgl_thunks",
     "../../platform/native:gles2",
   ]
 }
 
 group("gpu_onscreen") {
   public_deps = [
     ":MGL_onscreen",
   ]
@@ skipping 16 matching lines @@
 mojo_sdk_source_set("MGL_onscreen") {
   sources = [
     "MGL/mgl_onscreen.h",
   ]
 
   public_deps = [
     ":MGL",
   ]
 }
 
+mojo_sdk_source_set("MGL_signal_sync_point") {
+  sources = [
+    "MGL/mgl_signal_sync_point.h",
+  ]
+
+  public_deps = [
+    ":MGL",
+  ]
+}
+
 mojo_sdk_source_set("GLES2") {
   sources = [
     "GLES2/gl2.h",
     "GLES2/gl2ext.h",
     "GLES2/gl2mojo.h",
   ]
 
   public_deps = [
     ":KHR",
   ]
 }
 
 mojo_sdk_source_set("KHR") {
   sources = [
     "KHR/khrplatform.h",
   ]
 }