[tracing] Ignore tracing allocations in heap profiler

base/trace_event/heap_profiler_scoped_ignore.h

+// 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.
+
+#ifndef BASE_TRACE_EVENT_HEAP_PROFILER_SCOPED_IGNORE_H

[Primiano Tucci (use gerrit), 2016/04/21 19:47:32]

if you want feel free to call this file already heap_profiler.h
and then in another cl move the rest.

[ssid, 2016/04/22 04:57:12]

Done.

+#define BASE_TRACE_EVENT_HEAP_PROFILER_SCOPED_IGNORE_H
+
+#include "base/trace_event/heap_profiler_allocation_context_tracker.h"
+#include "base/trace_event/trace_event.h"

[Primiano Tucci (use gerrit), 2016/04/21 19:47:32]

you are including this only for INTERNAL_TRACE_UID right?
To be honest, since trace_event is a complex header, why not doing just (below)

ScopedIgnore heap_profiler_ignore#__LINE__  ?
Might be just simpler

[ssid, 2016/04/22 04:57:12]

This does not seem to work. I had to add macros similar to TRACE_EVENT_UID.
heap_profiler_ignore#__LINE__ gives: heap_profiler_ignore#40
With one level of indirection and ## it gives: heap_profiler_ignore__LINE__
if I write a # in second level it gives: heap_profiler_ignore"__LINE__"
With second level only it gives: heap_profiler_ignore40. 

I couldn't find a better way to do it. I am copying the TRACE_EVENT_UID
implementation.

+
+#define HEAP_PROFILER_SCOPED_IGNORE                                            \
+  base::trace_event::HeapProfilerScopedIgnore INTERNAL_TRACE_EVENT_UID(        \
+      heap_profiler_ignore);                                                   \
+  if (UNLIKELY(                                                                \
+          base::trace_event::AllocationContextTracker::capture_enabled())) {   \

[Primiano Tucci (use gerrit), 2016/04/21 19:47:32]

remove the curly braces and make this 
 if (UNLIKELY(....))
     ...GetInstanceForCurrentThread()->begin_ignore_scope()
without a trailing smicolon
so that when you write


HEAP_PROFILER_SCOPED_IGNORE;
it makes sense and you don't get warning about null statements.

[ssid, 2016/04/22 04:57:12]

Done.

+    base::trace_event::AllocationContextTracker::GetInstanceForCurrentThread() \
+        ->begin_ignore_scope();                                                \
+  }
+
+namespace base {
+namespace trace_event {
+
+// A scoped ignore event used to tell AllocationContextTracker to ignore all the

[Primiano Tucci (use gerrit), 2016/04/21 19:47:32]

s/AllocationCOntextTracker/the memory-infra heap profiler/

[ssid, 2016/04/22 04:57:12]

Done.

+// allocations in the scope. It is useful to exclude allocations made for
+// tracing from the heap profiler dumps. This class is to be used only using the
+// macro HEAP_PROFILER_SCOPED_IGNORE.
+class BASE_EXPORT HeapProfilerScopedIgnore {
+ public:
+  HeapProfilerScopedIgnore();
+  ~HeapProfilerScopedIgnore();
+};
+
+}  // namespace trace_event
+}  // namespace base
+
+#endif  // BASE_TRACE_EVENT_HEAP_PROFILER_SCOPED_IGNORE_H