Tag some of Mojo heap allocations for the heap profiler.

mojo/public/cpp/bindings/connector.h

 // Copyright 2013 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_PUBLIC_CPP_BINDINGS_CONNECTOR_H_
 #define MOJO_PUBLIC_CPP_BINDINGS_CONNECTOR_H_
 
 #include <memory>
 
 #include "base/callback.h"
@@ skipping 132 matching lines @@
   // callback.
   // It always returns false after CloseMessagePipe()/PassMessagePipe().
   bool during_sync_handle_watcher_callback() const {
     return sync_handle_watcher_callback_count_ > 0;
   }
 
   base::SingleThreadTaskRunner* task_runner() const {
     return task_runner_.get();
   }
 
+  void SetWatcherHeapProfilerTag(const std::string& tag);

[ssid, 2017/01/12 21:52:54]

const char* with a comment saying this must be a const string literal and not
dynamically allocated.

[Jay Civelli, 2017/01/13 01:09:27]

Done.

+
  private:
   // Callback of mojo::Watcher.
   void OnWatcherHandleReady(MojoResult result);
   // Callback of SyncHandleWatcher.
   void OnSyncHandleWatcherHandleReady(MojoResult result);
   void OnHandleReadyInternal(MojoResult result);
 
   void WaitToReadMore();
 
   // Returns false if it is impossible to receive more messages in the future.
@@ skipping 36 matching lines @@
   bool allow_woken_up_by_others_ = false;
   // If non-zero, currently the control flow is inside the sync handle watcher
   // callback.
   size_t sync_handle_watcher_callback_count_ = 0;
 
   base::ThreadChecker thread_checker_;
 
   base::Lock connected_lock_;
   bool connected_ = true;
 
+  // The tag to be used to track heap allocations performed by the watcher.

[Ken Rockot(use gerrit already), 2017/01/12 21:05:22]

nit: Not really allocations performed by the watcher

[Jay Civelli, 2017/01/13 01:09:27]

Clarified.

+  std::string heap_profiler_tag_;

[ssid, 2017/01/12 21:52:54]

Oh this should be const char*.
We do not store the strings in heap profiler so that we don't allocate more
memory for storing category names. It is better if we are tagged with only
strings in the binary. So, const char* everywhere.

[Jay Civelli, 2017/01/13 01:09:27]

Done.

+
   // Create a single weak ptr and use it everywhere, to avoid the malloc/free
   // cost of creating a new weak ptr whenever it is needed.
   // NOTE: This weak pointer is invalidated when the message pipe is closed or
   // transferred (i.e., when |connected_| is set to false).
   base::WeakPtr<Connector> weak_self_;
   base::WeakPtrFactory<Connector> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(Connector);
 };
 
 }  // namespace mojo
 
 #endif  // MOJO_PUBLIC_CPP_BINDINGS_CONNECTOR_H_