Tag some of Mojo heap allocations for the heap profiler.

mojo/public/cpp/system/watcher.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_PUBLIC_CPP_SYSTEM_WATCHER_H_
 #define MOJO_PUBLIC_CPP_SYSTEM_WATCHER_H_
 
 #include "base/callback.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
@@ skipping 18 matching lines @@
   //
   //   |MOJO_RESULT_OK|: One or more of the signals being watched is satisfied.
   //
   //   |MOJO_RESULT_FAILED_PRECONDITION|: None of the signals being watched can
   //       ever be satisfied again.
   //
   //   |MOJO_RESULT_CANCELLED|: The handle has been closed and the watch has
   //       been cancelled implicitly.
   using ReadyCallback = base::Callback<void(MojoResult result)>;
 
-  explicit Watcher(scoped_refptr<base::SingleThreadTaskRunner> runner =
-                       base::ThreadTaskRunnerHandle::Get());
+  Watcher(const tracked_objects::Location& from_here,
+          scoped_refptr<base::SingleThreadTaskRunner> runner =
+              base::ThreadTaskRunnerHandle::Get());
 
   // NOTE: This destructor automatically calls |Cancel()| if the Watcher is
   // still active.
   ~Watcher();
 
   // Indicates if the Watcher is currently watching a handle.
   bool IsWatching() const;
 
   // Starts watching |handle|. A Watcher may only watch one handle at a time,
   // but it is safe to call this more than once as long as the previous watch
@@ skipping 16 matching lines @@
                    MojoHandleSignals signals,
                    const ReadyCallback& callback);
 
   // Cancels the current watch. Once this returns, the callback previously
   // passed to |Start()| will never be called again for this Watcher.
   void Cancel();
 
   Handle handle() const { return handle_; }
   ReadyCallback ready_callback() const { return callback_; }
 
+ // Sets the tag used by the heap profiler.
+ // |tag| must be a const string literal.
+ void set_heap_profiler_tag(const char* heap_profiler_tag) {
+   heap_profiler_tag_ = heap_profiler_tag;
+ }
+
  private:
   void OnHandleReady(MojoResult result);
 
   static void CallOnHandleReady(uintptr_t context,
                                 MojoResult result,
                                 MojoHandleSignalsState signals_state,
                                 MojoWatchNotificationFlags flags);
 
   base::ThreadChecker thread_checker_;
 
@@ skipping 10 matching lines @@
   base::WeakPtr<Watcher> weak_self_;
 
   // Fields below must only be accessed on the Watcher's owning thread.
 
   // The handle currently under watch. Not owned.
   Handle handle_;
 
   // The callback to call when the handle is signaled.
   ReadyCallback callback_;
 
+  // Tag used to ID memory allocations that originated from notifications in
+  // this watcher.
+  const char* heap_profiler_tag_ = nullptr;
+
   base::WeakPtrFactory<Watcher> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(Watcher);
 };
 
 }  // namespace mojo
 
 #endif  // MOJO_PUBLIC_CPP_SYSTEM_WATCHER_H_