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..20a6e3015d647aaad1272e3c36cc03e93d2c8eb6 100644
--- a/base/trace_event/heap_profiler_allocation_context_tracker.h
+++ b/base/trace_event/heap_profiler_allocation_context_tracker.h
@@ -43,22 +43,25 @@ class BASE_EXPORT AllocationContextTracker {
     return subtle::Acquire_Load(&capture_enabled_) != 0;
   }
 
+  // Returns the thread-local instance, creating one if necessary. Returns
+  // always a valid instance, unless it is called re-entrantly, in which case
+  // returns nullptr in the nested calls.
+  static AllocationContextTracker* GetInstanceForCurrentThread();
+
   // Pushes a frame onto the thread-local pseudo stack.
-  static void PushPseudoStackFrame(StackFrame frame);
+  void PushPseudoStackFrame(StackFrame frame);
 
   // Pops a frame from the thread-local pseudo stack.
-  static void PopPseudoStackFrame(StackFrame frame);
+  void PopPseudoStackFrame(StackFrame frame);
 
   // Returns a snapshot of the current thread-local context.
-  static AllocationContext GetContextSnapshot();
+  AllocationContext GetContextSnapshot();
 
   ~AllocationContextTracker();
 
  private:
   AllocationContextTracker();
 
-  static AllocationContextTracker* GetThreadLocalTracker();
-
   static subtle::Atomic32 capture_enabled_;
 
   // The pseudo stack where frames are |TRACE_EVENT| names.