Add TRACE_EVENT_IS_NEW_TRACE as a way to snapshot objects at start of recording

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/bind.h"
 #include "base/debug/leak_annotations.h"
@@ skipping 755 matching lines @@
     }
   }
   if (!(ret & RECORD_UNTIL_FULL) && !(ret & RECORD_CONTINUOUSLY))
     ret |= RECORD_UNTIL_FULL;  // Default when no options are specified.
 
   return static_cast<Options>(ret);
 }
 
 TraceLog::TraceLog()
     : enable_count_(0),
+      num_traces_recorded_(0),
       logged_events_(NULL),
       dispatching_to_observer_list_(false),
       watch_category_(NULL),
       trace_options_(RECORD_UNTIL_FULL),
       sampling_thread_handle_(0),
       category_filter_(CategoryFilter::kDefaultCategoryFilterString) {
   // Trace is enabled or disabled on one thread while other threads are
   // accessing the enabled flag. We don't care whether edge-case events are
   // traced or not, so we allow races on the enabled flag to keep the trace
   // macros fast.
@@ skipping 134 matching lines @@
     trace_options_ = options;
     logged_events_.reset(GetTraceBuffer());
   }
 
   if (dispatching_to_observer_list_) {
     DLOG(ERROR) <<
         "Cannot manipulate TraceLog::Enabled state from an observer.";
     return;
   }
 
+  num_traces_recorded_++;
+
   dispatching_to_observer_list_ = true;
   FOR_EACH_OBSERVER(EnabledStateChangedObserver, enabled_state_observer_list_,
                     OnTraceLogWillEnable());
   dispatching_to_observer_list_ = false;
 
   category_filter_ = CategoryFilter(category_filter);
   EnableIncludedCategoryGroups();
 
   // Not supported in split-dll build. http://crbug.com/237249
 #if !defined(CHROME_SPLIT_DLL)
@@ skipping 54 matching lines @@
   dispatching_to_observer_list_ = false;
 
   category_filter_.Clear();
   watch_category_ = NULL;
   watch_event_name_ = "";
   for (int i = 0; i < g_category_index; i++)
     SetCategoryGroupEnabled(i, false);
   AddThreadNameMetadataEvents();
 }
 
+int TraceLog::GetNumTracesRecorded() {
+  AutoLock lock(lock_);
+  if (enable_count_ == 0)
+    return -1;
+  return num_traces_recorded_;
+}
+
 void TraceLog::AddEnabledStateObserver(EnabledStateChangedObserver* listener) {
   enabled_state_observer_list_.AddObserver(listener);
 }
 
 void TraceLog::RemoveEnabledStateObserver(
     EnabledStateChangedObserver* listener) {
   enabled_state_observer_list_.RemoveObserver(listener);
 }
 
 float TraceLog::GetBufferPercentFull() const {
@@ skipping 490 matching lines @@
         0,                       // num_args
         NULL,                    // arg_names
         NULL,                    // arg_types
         NULL,                    // arg_values
         NULL,                    // convertable values
         TRACE_EVENT_FLAG_NONE);  // flags
   }
 }
 
 }  // namespace trace_event_internal
-