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

content/browser/tracing/tracing_controller_impl.h

Index: content/browser/tracing/tracing_controller_impl.h
diff --git a/content/browser/tracing/tracing_controller_impl.h b/content/browser/tracing/tracing_controller_impl.h
index 9bd84200d45f276f9c5b84886afa5d9290964818..2b866faa6cb28a8f61ddd2243fa1ba0cadd9ca4d 100644
--- a/content/browser/tracing/tracing_controller_impl.h
+++ b/content/browser/tracing/tracing_controller_impl.h
@@ -43,8 +43,8 @@ class TracingControllerImpl : public TracingController {
       base::debug::TraceOptions* out_trace_options) override;
   bool CaptureMonitoringSnapshot(
       const scoped_refptr<TraceDataSink>& sink) override;
-  bool GetTraceBufferPercentFull(
-      const GetTraceBufferPercentFullCallback& callback) override;
+  bool GetTraceBufferUsage(
+      const GetTraceBufferUsageCallback& callback) override;
   bool SetWatchEvent(const std::string& category_name,
                      const std::string& event_name,
                      const WatchEventCallback& callback) override;
@@ -78,8 +78,8 @@ class TracingControllerImpl : public TracingController {
     return is_monitoring_ && !monitoring_data_sink_.get();
   }
 
-  bool can_get_trace_buffer_percent_full() const {
-    return pending_trace_buffer_percent_full_callback_.is_null();
+  bool can_get_trace_buffer_usage() const {
+    return pending_trace_buffer_usage_callback_.is_null();
   }
 
   bool can_cancel_watch_event() const {
@@ -116,9 +116,9 @@ class TracingControllerImpl : public TracingController {
   void OnCaptureMonitoringSnapshotAcked(
       TraceMessageFilter* trace_message_filter);
 
-  void OnTraceBufferPercentFullReply(
-      TraceMessageFilter* trace_message_filter,
-      float percent_full);
+  void OnTraceBufferUsageReply(TraceMessageFilter* trace_message_filter,
+                               size_t event_capacity,
+                               size_t event_count);
 
   void OnWatchEventMatched();
 
@@ -148,10 +148,11 @@ class TracingControllerImpl : public TracingController {
   // Pending acks for CaptureMonitoringSnapshot.
   int pending_capture_monitoring_snapshot_ack_count_;
   TraceMessageFilterSet pending_capture_monitoring_filters_;
-  // Pending acks for GetTraceBufferPercentFull.
-  int pending_trace_buffer_percent_full_ack_count_;
-  TraceMessageFilterSet pending_trace_buffer_percent_full_filters_;
-  float maximum_trace_buffer_percent_full_;
+  // Pending acks for GetTraceBufferUsage.
+  int pending_trace_buffer_usage_ack_count_;
+  TraceMessageFilterSet pending_trace_buffer_usage_filters_;
+  float maximum_trace_buffer_usage_;
+  size_t approximate_event_count_;
 
 #if defined(OS_CHROMEOS) || defined(OS_WIN)
   bool is_system_tracing_;
@@ -161,7 +162,7 @@ class TracingControllerImpl : public TracingController {
   base::debug::TraceOptions trace_options_;
 
   GetCategoriesDoneCallback pending_get_categories_done_callback_;
-  GetTraceBufferPercentFullCallback pending_trace_buffer_percent_full_callback_;
+  GetTraceBufferUsageCallback pending_trace_buffer_usage_callback_;
 
   std::string watch_category_name_;
   std::string watch_event_name_;