Add MGL entry points and port spinning_cube to use them

mojo/gles2/BUILD.gn

 # Copyright 2014 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/public/tools/bindings/mojom.gni")
 
 config("mojo_use_gles2") {
   defines = [ "MOJO_USE_GLES2_IMPL" ]
 }
 
 config("gles2_use_mojo") {
   defines = [ "GLES2_USE_MOJO" ]
 }
 
 source_set("gles2") {
   sources = [
     "command_buffer_client_impl.cc",
     "command_buffer_client_impl.h",
-    "gles2_impl.cc",
     "gles2_context.cc",
     "gles2_context.h",
+    "gles2_impl.cc",
   ]
 
   defines = [
     "GL_GLEXT_PROTOTYPES",
     "MOJO_GLES2_IMPLEMENTATION",
   ]
 
   configs += [
     ":gles2_use_mojo",
     ":mojo_use_gles2",
@@ skipping 11 matching lines @@
     "//gpu/command_buffer/common",
     "//mojo/environment:chromium",
     "//mojo/public/c/gles2:headers",
     "//mojo/public/c/system",
     "//mojo/public/cpp/bindings",
     "//mojo/public/cpp/system",
     "//mojo/services/gpu/public/interfaces",
     "//services/gles2:lib",
   ]
 }
+
+source_set("mgl") {
+  sources = [
+    "mgl_impl.cc",
+  ]
+
+  configs += [ ":gles2_use_mojo" ]
+
+  deps = [
+    ":gles2",
+    "//mojo/public/c/gles2:headers",
+    "//mojo/public/c/gpu:MGL",
+    "//mojo/public/c/gpu:MGL_onscreen",
+    "//mojo/public/cpp/system",
+  ]
+}