[tracing] Add support for profiling trace events

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/trace_event/heap_profiler_allocation_context.h"
@@ skipping 42 matching lines @@
           ->GetContextSnapshot();
 
   for (StackFrame frame : ctx.backtrace.frames)
     ASSERT_EQ(nullptr, frame);
 }
 
 class AllocationContextTrackerTest : public testing::Test {
  public:
   void SetUp() override {
     TraceConfig config("");
+    AllocationContextTracker::SetCaptureEnabled(true);
     TraceLog::GetInstance()->SetEnabled(config, TraceLog::RECORDING_MODE);
-    AllocationContextTracker::SetCaptureEnabled(true);
   }
 
   void TearDown() override {
     AllocationContextTracker::SetCaptureEnabled(false);
     TraceLog::GetInstance()->SetDisabled();
   }
 };
 
 // Check that |TRACE_EVENT| macros push and pop to the pseudo stack correctly.
 // Also check that |GetContextSnapshot| fills the backtrace with null pointers
@@ skipping 149 matching lines @@
     AllocationContext ctx =
         AllocationContextTracker::GetInstanceForCurrentThread()
             ->GetContextSnapshot();
     ASSERT_EQ(kCupcake, ctx.backtrace.frames[0]);
     ASSERT_EQ(kFroyo, ctx.backtrace.frames[11]);
   }
 }
 
 }  // namespace trace_event
 }  // namespace base