Add some Mojo C thunks used by cc when turning on impl-side painting.

mojo/public/platform/native/gles2_impl_chromium_copy_texture_thunks.cc

+// 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.
+
+#include "mojo/public/platform/native/gles2_impl_chromium_copy_texture_thunks.h"
+
+#include <assert.h>
+
+#include "mojo/public/platform/native/thunk_export.h"
+
+extern "C" {
+static MojoGLES2ImplChromiumCopyTextureThunks g_impl_chromium_copy_texture_thunks = {0};
+
+#define VISIT_GL_CALL(Function, ReturnType, PARAMETERS, ARGUMENTS) \
+  ReturnType gl##Function PARAMETERS {                             \
+    assert(g_impl_chromium_copy_texture_thunks.Function);             \
+    return g_impl_chromium_copy_texture_thunks.Function ARGUMENTS;    \
+  }
+#include "mojo/public/c/gles2/gles2_call_visitor_chromium_copy_texture_autogen.h"
+#undef VISIT_GL_CALL
+
+extern "C" THUNK_EXPORT size_t MojoSetGLES2ImplChromiumCopyTextureThunks(
+    const MojoGLES2ImplChromiumCopyTextureThunks*
+        gles2_impl_chromium_copy_texture_thunks) {
+  if (gles2_impl_chromium_copy_texture_thunks->size >=
+      sizeof(g_impl_chromium_copy_texture_thunks))
+    g_impl_chromium_copy_texture_thunks = *gles2_impl_chromium_copy_texture_thunks;
+  return sizeof(g_impl_chromium_copy_texture_thunks);
+}
+
+}  // extern "C"