[tracing] Ignore tracing allocations in heap profiler

base/trace_event/heap_profiler_allocation_context_tracker_unittest.cc

 // 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.
 
 #include <stddef.h>
 
 #include <iterator>
 
 #include "base/memory/ref_counted.h"
 #include "base/pending_task.h"
+#include "base/trace_event/heap_profiler.h"
 #include "base/trace_event/heap_profiler_allocation_context.h"
 #include "base/trace_event/heap_profiler_allocation_context_tracker.h"
 #include "base/trace_event/trace_event.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace base {
 namespace trace_event {
 
 // Define all strings once, because the pseudo stack requires pointer equality,
 // and string interning is unreliable.
@@ skipping 250 matching lines @@
     ASSERT_EQ(kContext2, ctx2.type_name);
   }
 
   // Type should be nullptr without task event.
   AllocationContext ctx =
       AllocationContextTracker::GetInstanceForCurrentThread()
           ->GetContextSnapshot();
   ASSERT_FALSE(ctx.type_name);
 }
 
+TEST_F(AllocationContextTrackerTest, IgnoreAllocationTest) {
+  TRACE_EVENT0("Testing", kCupcake);
+  TRACE_EVENT0("Testing", kDonut);
+  HEAP_PROFILER_SCOPED_IGNORE;
+  AllocationContext ctx =
+      AllocationContextTracker::GetInstanceForCurrentThread()
+          ->GetContextSnapshot();
+  const StringPiece kTracingOverhead("tracing_overhead");
+  ASSERT_EQ(kTracingOverhead,
+            static_cast<const char*>(ctx.backtrace.frames[0].value));
+  ASSERT_EQ(1u, ctx.backtrace.frame_count);
+}
+
 }  // namespace trace_event
 }  // namespace base