[mojo-edk] Cache the context thread-local in the RequestContext.

mojo/edk/system/request_context.h

 // Copyright 2016 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.
 
 #ifndef MOJO_EDK_SYSTEM_REQUEST_CONTEXT_H_
 #define MOJO_EDK_SYSTEM_REQUEST_CONTEXT_H_
 
 #include "base/containers/stack_container.h"
 #include "base/macros.h"
 #include "mojo/edk/system/handle_signals_state.h"
 #include "mojo/edk/system/watcher.h"
 
+namespace base {
+template<typename T> class ThreadLocalPointer;
+}
+
 namespace mojo {
 namespace edk {
 
 // A RequestContext is a thread-local object which exists for the duration of
 // a single system API call. It is constructed immediately upon EDK entry and
 // destructed immediately before returning to the caller, after any internal
 // locks have been released.
 //
 // NOTE: It is legal to construct a RequestContext while another one already
 // exists on the current thread, but it is not safe to use the nested context
@@ skipping 43 matching lines @@
   static const size_t kStaticWatchFinalizersCapacity = 4;
 
   using WatchNotifyFinalizerList =
       base::StackVector<WatchNotifyFinalizer, kStaticWatchFinalizersCapacity>;
   using WatchCancelFinalizerList =
       base::StackVector<scoped_refptr<Watcher>, kStaticWatchFinalizersCapacity>;
 
   WatchNotifyFinalizerList watch_notify_finalizers_;
   WatchCancelFinalizerList watch_cancel_finalizers_;
 
+  // Pointer to the TLS context. Although this can easily be accessed via the
+  // global LazyInstance, accessing a LazyInstance has a large cost relative to
+  // the rest of this class and its usages.
+  base::ThreadLocalPointer<RequestContext>* tls_context_;

[Ken Rockot(use gerrit already), 2016/03/07 04:25:00]

Hmm, couldn't this just be a raw pointer?

+
   DISALLOW_COPY_AND_ASSIGN(RequestContext);
 };
 
 }  // namespace edk
 }  // namespace mojo
 
 #endif  // MOJO_EDK_SYSTEM_REQUEST_CONTEXT_H_