Add granular file tracing.

base/trace_event/trace_event_impl.cc

Index: base/trace_event/trace_event_impl.cc
diff --git a/base/trace_event/trace_event_impl.cc b/base/trace_event/trace_event_impl.cc
index cbeeeabb0cbc833611d22d85c23781e562fe3f5e..a8fc22572a9714d11a2a3da3dd7291dc36c99719 100644
--- a/base/trace_event/trace_event_impl.cc
+++ b/base/trace_event/trace_event_impl.cc
@@ -306,7 +306,7 @@ class TraceBufferVector : public TraceBuffer {
 
   scoped_ptr<TraceBufferChunk> GetChunk(size_t* index) override {
     // This function may be called when adding normal events or indirectly from
-    // AddMetadataEventsWhileLocked(). We can not DECHECK(!IsFull()) because we
+    // AddMetadataEventsWhileLocked(). We can not DCHECK(!IsFull()) because we
     // have to add the metadata events and flush thread-local buffers even if
     // the buffer is full.
     *index = chunks_.size();
@@ -724,7 +724,8 @@ void TraceEvent::AppendAsJSON(std::string* out) const {
   }
   *out += "}";
 
-  if (phase_ == TRACE_EVENT_PHASE_COMPLETE) {
+  if (phase_ == TRACE_EVENT_PHASE_COMPLETE ||
+      phase_ == TRACE_EVENT_PHASE_NESTABLE_ASYNC_COMPLETE) {
     int64 duration = duration_.ToInternalValue();
     if (duration != -1)
       StringAppendF(out, ",\"dur\":%" PRId64, duration);
@@ -2077,6 +2078,7 @@ std::string TraceLog::EventToConsoleMessage(unsigned char phase,
   // The caller should translate TRACE_EVENT_PHASE_COMPLETE to
   // TRACE_EVENT_PHASE_BEGIN or TRACE_EVENT_END.
   DCHECK(phase != TRACE_EVENT_PHASE_COMPLETE);
+  DCHECK(phase != TRACE_EVENT_PHASE_NESTABLE_ASYNC_COMPLETE);
 
   TimeDelta duration;
   int thread_id = trace_event ?
@@ -2159,7 +2161,8 @@ void TraceLog::UpdateTraceEventDuration(
 
     TraceEvent* trace_event = GetEventByHandleInternal(handle, &lock);
     if (trace_event) {
-      DCHECK(trace_event->phase() == TRACE_EVENT_PHASE_COMPLETE);
+      DCHECK(trace_event->phase() == TRACE_EVENT_PHASE_COMPLETE ||
+             trace_event->phase() == TRACE_EVENT_PHASE_NESTABLE_ASYNC_COMPLETE);
       trace_event->UpdateDuration(now, thread_now);
 #if defined(OS_ANDROID)
       trace_event->SendToATrace();