Add helper classes to for managing shared buffers.

mojo/services/media/common/cpp/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("//build/module_args/mojo.gni")
 import("$mojo_sdk_root/mojo/public/mojo_sdk.gni")
 
 mojo_sdk_source_set("cpp") {
   restrict_external_deps = false
   sources = [
     "circular_buffer_media_pipe_adapter.cc",
     "circular_buffer_media_pipe_adapter.h",
+    "fifo_allocator.cc",
+    "fifo_allocator.h",
     "linear_transform.cc",
     "linear_transform.h",
     "local_time.h",
+    "mapped_shared_buffer.cc",
+    "mapped_shared_buffer.h",
+    "shared_media_buffer_allocator.cc",
+    "shared_media_buffer_allocator.h",
   ]
 
   if (is_posix) {
     sources += [
       "platform/posix/local_time.cc",
       "platform/posix/local_time.h",
     ]
   } else {
     sources += [ "platform/generic/local_time.h" ]
   }
 
   deps = [
     "$mojo_sdk_root/mojo/public/cpp/environment",
     "$mojo_sdk_root/mojo/public/cpp/utility",
     "$mojo_sdk_root/mojo/services/media/common/interfaces",
   ]
 }