Use TracingController for startup tracing

base/debug/trace_event_impl.cc

 // Copyright (c) 2012 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 "base/debug/trace_event_impl.h"
 
 #include <algorithm>
 
 #include "base/base_switches.h"
 #include "base/bind.h"
@@ skipping 1516 matching lines @@
 // 2. If thread_message_loops_ is not empty, threadA posts task to each message
 //    loop to flush the thread local buffers; otherwise finish the flush;
 // 3. FlushCurrentThread() deletes the thread local event buffer:
 //    - The last batch of events of the thread are flushed into the main buffer;
 //    - The message loop will be removed from thread_message_loops_;
 //    If this is the last message loop, finish the flush;
 // 4. If any thread hasn't finish its flush in time, finish the flush.
 void TraceLog::Flush(const TraceLog::OutputCallback& cb) {
   if (IsEnabled()) {
     // Can't flush when tracing is enabled because otherwise PostTask would
-    // - it generates more trace events;
-    // - it deschedules the calling thread on some platforms causing inaccurate
+    // - generate more trace events;
+    // - deschedule the calling thread on some platforms causing inaccurate
     //   timing of the trace events.
     scoped_refptr<RefCountedString> empty_result = new RefCountedString;
     if (!cb.is_null())
       cb.Run(empty_result, false);
     LOG(WARNING) << "Ignored TraceLog::Flush called when tracing is enabled";
     return;
   }
 
   int generation = this->generation();
   {
@@ skipping 123 matching lines @@
          thread_message_loops_.begin();
          it != thread_message_loops_.end(); ++it) {
       LOG(WARNING) << "Thread: " << (*it)->thread_name();
     }
   }
   FinishFlush(generation);
 }
 
 void TraceLog::FlushButLeaveBufferIntact(
     const TraceLog::OutputCallback& flush_output_callback) {
-  if (!sampling_thread_)
-      return;
-
   scoped_ptr<TraceBuffer> previous_logged_events;
   {
     AutoLock lock(lock_);
     AddMetadataEventsWhileLocked();
     if (thread_shared_chunk_) {
       // Return the chunk to the main buffer to flush the sampling data.
       logged_events_->ReturnChunk(thread_shared_chunk_index_,
                                   thread_shared_chunk_.Pass());
     }
     previous_logged_events = logged_events_->CloneForIteration().Pass();
@@ skipping 633 matching lines @@
 }
 
 ScopedTraceBinaryEfficient::~ScopedTraceBinaryEfficient() {
   if (*category_group_enabled_) {
     TRACE_EVENT_API_UPDATE_TRACE_EVENT_DURATION(category_group_enabled_,
                                                 name_, event_handle_);
   }
 }
 
 }  // namespace trace_event_internal