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

content/browser/tracing/tracing_controller_impl.cc

Index: content/browser/tracing/tracing_controller_impl.cc
diff --git a/content/browser/tracing/tracing_controller_impl.cc b/content/browser/tracing/tracing_controller_impl.cc
index 3e8e1ac7cd1c0fc2d5aa5df1fbf84e88b5f626d9..2a1ceaafee577101a9ef230cdaac3e3101596a04 100644
--- a/content/browser/tracing/tracing_controller_impl.cc
+++ b/content/browser/tracing/tracing_controller_impl.cc
@@ -162,18 +162,19 @@ TracingController* TracingController::GetInstance() {
   return TracingControllerImpl::GetInstance();
 }
 
-TracingControllerImpl::TracingControllerImpl() :
-    pending_disable_recording_ack_count_(0),
-    pending_capture_monitoring_snapshot_ack_count_(0),
-    pending_trace_buffer_percent_full_ack_count_(0),
-    maximum_trace_buffer_percent_full_(0),
+TracingControllerImpl::TracingControllerImpl()
+    : pending_disable_recording_ack_count_(0),
+      pending_capture_monitoring_snapshot_ack_count_(0),
+      pending_trace_buffer_percent_full_ack_count_(0),
+      maximum_trace_buffer_percent_full_(0),
+      approximate_event_count_(0),
     // Tracing may have been enabled by ContentMainRunner if kTraceStartup
     // is specified in command line.
 #if defined(OS_CHROMEOS) || defined(OS_WIN)
-    is_system_tracing_(false),
+      is_system_tracing_(false),
 #endif
-    is_recording_(TraceLog::GetInstance()->IsEnabled()),
-    is_monitoring_(false) {
+      is_recording_(TraceLog::GetInstance()->IsEnabled()),
+      is_monitoring_(false) {
 }
 
 TracingControllerImpl::~TracingControllerImpl() {
@@ -499,8 +500,8 @@ bool TracingControllerImpl::CaptureMonitoringSnapshot(
   return true;
 }
 
-bool TracingControllerImpl::GetTraceBufferPercentFull(
-    const GetTraceBufferPercentFullCallback& callback) {
+bool TracingControllerImpl::GetTraceBufferUsage(
+    const GetTraceBufferUsageCallback& callback) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 
   if (!can_get_trace_buffer_percent_full() || callback.is_null())
@@ -513,20 +514,24 @@ bool TracingControllerImpl::GetTraceBufferPercentFull(
       trace_message_filters_.size() + 1;
   pending_trace_buffer_percent_full_filters_ = trace_message_filters_;
   maximum_trace_buffer_percent_full_ = 0;
+  approximate_event_count_ = 0;
 
-  // Call OnTraceBufferPercentFullReply unconditionally for the browser process.
+  TraceLog::BufferUsage buffer_usage =
+      TraceLog::GetInstance()->GetBufferUsage();
+  // Call OnTraceBufferUsageReply unconditionally for the browser process.
   // This will result in immediate execution of the callback if there are no
   // child processes.
-  BrowserThread::PostTask(BrowserThread::UI, FROM_HERE,
-      base::Bind(&TracingControllerImpl::OnTraceBufferPercentFullReply,
-                  base::Unretained(this),
-                  scoped_refptr<TraceMessageFilter>(),
-                  TraceLog::GetInstance()->GetBufferPercentFull()));
+  BrowserThread::PostTask(
+      BrowserThread::UI, FROM_HERE,
+      base::Bind(&TracingControllerImpl::OnTraceBufferUsageReply,
+                 base::Unretained(this), scoped_refptr<TraceMessageFilter>(),
+                 buffer_usage.percent_full,
+                 buffer_usage.approximate_event_count));
 
   // Notify all child processes.
   for (TraceMessageFilterSet::iterator it = trace_message_filters_.begin();
       it != trace_message_filters_.end(); ++it) {
-    it->get()->SendGetTraceBufferPercentFull();
+    it->get()->SendGetTraceBufferUsage();
   }
   return true;
 }
@@ -636,11 +641,11 @@ void TracingControllerImpl::RemoveTraceMessageFilter(
     TraceMessageFilterSet::const_iterator it =
         pending_trace_buffer_percent_full_filters_.find(trace_message_filter);
     if (it != pending_trace_buffer_percent_full_filters_.end()) {
-      BrowserThread::PostTask(BrowserThread::UI, FROM_HERE,
-          base::Bind(&TracingControllerImpl::OnTraceBufferPercentFullReply,
+      BrowserThread::PostTask(
+          BrowserThread::UI, FROM_HERE,
+          base::Bind(&TracingControllerImpl::OnTraceBufferUsageReply,
                      base::Unretained(this),
-                     make_scoped_refptr(trace_message_filter),
-                     0));
+                     make_scoped_refptr(trace_message_filter), 0, 0));
     }
   }
 
@@ -815,15 +820,17 @@ void TracingControllerImpl::OnLocalMonitoringTraceDataCollected(
   OnCaptureMonitoringSnapshotAcked(NULL);
 }
 
-void TracingControllerImpl::OnTraceBufferPercentFullReply(
+void TracingControllerImpl::OnTraceBufferUsageReply(
     TraceMessageFilter* trace_message_filter,
-    float percent_full) {
+    float percent_full,
+    size_t approximate_event_count) {
   if (!BrowserThread::CurrentlyOn(BrowserThread::UI)) {
-    BrowserThread::PostTask(BrowserThread::UI, FROM_HERE,
-        base::Bind(&TracingControllerImpl::OnTraceBufferPercentFullReply,
+    BrowserThread::PostTask(
+        BrowserThread::UI, FROM_HERE,
+        base::Bind(&TracingControllerImpl::OnTraceBufferUsageReply,
                    base::Unretained(this),
-                   make_scoped_refptr(trace_message_filter),
-                   percent_full));
+                   make_scoped_refptr(trace_message_filter), percent_full,
+                   approximate_event_count));
     return;
   }
 
@@ -838,11 +845,12 @@ void TracingControllerImpl::OnTraceBufferPercentFullReply(
 
   maximum_trace_buffer_percent_full_ =
       std::max(maximum_trace_buffer_percent_full_, percent_full);
+  approximate_event_count_ += approximate_event_count;
 
   if (--pending_trace_buffer_percent_full_ack_count_ == 0) {
     // Trigger callback if one is set.
     pending_trace_buffer_percent_full_callback_.Run(
-        maximum_trace_buffer_percent_full_);
+        maximum_trace_buffer_percent_full_, approximate_event_count_);
     pending_trace_buffer_percent_full_callback_.Reset();
   }
 }