tracing: add dump provider for malloc heap profiler

base/trace_event/heap_profiler_allocation_context_tracker.h

Index: base/trace_event/heap_profiler_allocation_context_tracker.h
diff --git a/base/trace_event/heap_profiler_allocation_context_tracker.h b/base/trace_event/heap_profiler_allocation_context_tracker.h
index 9c9a3132abab1e395a94d5632dc253845f43efa4..83912ce3cc232434fa2c937d9e21a958152b9c61 100644
--- a/base/trace_event/heap_profiler_allocation_context_tracker.h
+++ b/base/trace_event/heap_profiler_allocation_context_tracker.h
@@ -23,11 +23,23 @@ namespace trace_event {
 // details.
 class BASE_EXPORT AllocationContextTracker {
  public:
+  enum InitializationState { kNotInitialized = 0, kInitializing, kInitialized };
+
   // Globally enables capturing allocation context.
   // TODO(ruuda): Should this be replaced by |EnableCapturing| in the future?
   // Or at least have something that guards agains enable -> disable -> enable?
   static void SetCaptureEnabled(bool enabled);
 
+  // Exposes the initialization state of the tracker. This is to avoid
+  // re-entrancy in the malloc heap profiler, that will lazy initialize the

[petrcermak, 2016/03/11 11:09:23]

nit: s/that/which/ (you can't have "that" after a comma, which should stay here
in this case)

[petrcermak, 2016/03/11 11:09:23]

nit: s/lazy/lazily/

[Primiano Tucci (use gerrit), 2016/03/11 13:57:57]

Done.

[Primiano Tucci (use gerrit), 2016/03/11 13:57:57]

Done.

+  // thread-local context trackes on the first malloc seen, causing a nested

[petrcermak, 2016/03/11 11:09:23]

s/trackes/trackers/

[petrcermak, 2016/03/11 11:09:23]

supernit: wouldn't "first encountered malloc" read a little better?

[Primiano Tucci (use gerrit), 2016/03/11 13:57:57]

Done.

[Primiano Tucci (use gerrit), 2016/03/11 13:57:57]

actually was "tracker" , just typoed r/s

+  // allocation.
+  static InitializationState GetStateForCurrentThread();
+
+  // Enforces the initialization of the tracker. Subsequent calls to the other
+  // methods of this class are supposed to not cause any further malloc/new.
+  static AllocationContextTracker* InitializeForCurrentThread();
+
   // Returns whether capturing allocation context is enabled globally.
   inline static bool capture_enabled() {
     // A little lag after heap profiling is enabled or disabled is fine, it is