Move stash_backend into extensions/browser/mojo.

extensions/common/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("//build/config/features.gni")
 import("//mojo/public/tools/bindings/mojom.gni")
 
 # GYP version: extensions/extensions.gyp:extensions_common_constants
 source_set("common_constants") {
   sources = [
     "constants.cc",
     "constants.h",
   ]
 
   if (is_win) {
     cflags = [
       "/wd4267", # TODO(jschuh): crbug.com/167187 fix size_t to int truncations.
     ]
   }
 }
 
 if (enable_extensions) {
 
 mojom("mojo") {
   sources = [
     "mojo/keep_alive.mojom",
-    "stash.mojom",
+    "mojo/stash.mojom",
   ]
 }
 
 
 # GYP version: extensions/extensions.gyp:extensions_common
 source_set("common") {
   sources = [
     "api/messaging/message.h",
     "api/bluetooth/bluetooth_manifest_data.cc",
     "api/bluetooth/bluetooth_manifest_data.h",
@@ skipping 214 matching lines @@
   }
 
   if (is_win) {
     cflags = [
       "/wd4267", # TODO(jschuh): crbug.com/167187 fix size_t to int truncations.
     ]
   }
 }
 
 } # enable_extensions