Report trace buffer usage as number of events, not only percentage

content/browser/tracing/trace_message_filter.h

Index: content/browser/tracing/trace_message_filter.h
diff --git a/content/browser/tracing/trace_message_filter.h b/content/browser/tracing/trace_message_filter.h
index 3d12d76d300d23f497517afcafa419adcf15511d..37e3d9df3bec54744c7b1ca8ee0f41556e10c710 100644
--- a/content/browser/tracing/trace_message_filter.h
+++ b/content/browser/tracing/trace_message_filter.h
@@ -31,7 +31,7 @@ class TraceMessageFilter : public BrowserMessageFilter {
                             const base::debug::TraceOptions& options);
   void SendDisableMonitoring();
   void SendCaptureMonitoringSnapshot();
-  void SendGetTraceBufferPercentFull();
+  void SendGetTraceBufferUsage();
   void SendSetWatchEvent(const std::string& category_name,
                          const std::string& event_name);
   void SendCancelWatchEvent();
@@ -45,7 +45,8 @@ class TraceMessageFilter : public BrowserMessageFilter {
   void OnEndTracingAck(const std::vector<std::string>& known_categories);
   void OnCaptureMonitoringSnapshotAcked();
   void OnWatchEventMatched();
-  void OnTraceBufferPercentFullReply(float percent_full);
+  void OnTraceBufferUsageReply(float percent_full,
+                               size_t approximate_event_count);
   void OnTraceDataCollected(const std::string& data);
   void OnMonitoringTraceDataCollected(const std::string& data);
 
@@ -56,7 +57,7 @@ class TraceMessageFilter : public BrowserMessageFilter {
   bool is_awaiting_end_ack_;
   // Awaiting ack for previously sent SendCaptureMonitoringSnapshot
   bool is_awaiting_capture_monitoring_snapshot_ack_;
-  // Awaiting ack for previously sent SendGetTraceBufferPercentFull
+  // Awaiting ack for previously sent SendGetTraceBufferUsage
   bool is_awaiting_buffer_percent_full_ack_;
 
   DISALLOW_COPY_AND_ASSIGN(TraceMessageFilter);