Restructure public side of gpu service.

mojo/services/gpu/public/interfaces/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")
 
-mojom("gpu") {
+mojom("interfaces") {
   sources = [
     "command_buffer.mojom",
     "gpu.mojom",
     "gpu_capabilities.mojom",
     "viewport_parameter_listener.mojom",
   ]
 
   deps = [
     "//mojo/services/geometry/public/interfaces",
   ]
 }