Fix --trace-startup.

Some subprocesses handle --trace-startup by themselves to start
tracing as early as possible if the switch presents. However, previously
TraceController would enable tracing of the subprocess again by sending
TracingMsg_BeginTracing when it knew a new subprocess has been started.
This caused tracing of the subprocess not to be properly stopped and
flushed when startup tracing is ended.

Changes:
- Pass tracing_startup parameter through TracingMsg_BeginTracing;
  subprocess won't start tracing again if tracing_startup is true
  and tracing has already been started;
- Don't pass --trace-startup to renderer if startup tracing has
  already finished.

BUG=310395

Review URL: https://codereview.chromium.org/48903003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@231971 0039d316-1c4b-4281-b951-d872f2087c98

3 files changed, 16 insertions, 7 deletions

diff --git a/components/tracing/child_trace_message_filter.cc b/components/tracing/child_trace_message_filter.cc
index 9925f3f..721c676 100644
--- a/components/tracing/child_trace_message_filter.cc
+++ b/components/tracing/child_trace_message_filter.cc
@@ -52,7 +52,8 @@ ChildTraceMessageFilter::~ChildTraceMessageFilter() {}
 void ChildTraceMessageFilter::OnBeginTracing(
     const std::string& category_filter_str,
     base::TimeTicks browser_time,
-    int options) {
+    int options,
+    bool tracing_startup) {
 #if defined(__native_client__)
   // NaCl and system times are offset by a bit, so subtract some time from
   // the captured timestamps. The value might be off by a bit due to messaging
@@ -61,9 +62,15 @@ void ChildTraceMessageFilter::OnBeginTracing(
       browser_time;
   TraceLog::GetInstance()->SetTimeOffset(time_offset);
 #endif
-  TraceLog::GetInstance()->SetEnabled(
-      base::debug::CategoryFilter(category_filter_str),
-      static_cast<base::debug::TraceLog::Options>(options));
+
+  // Some subprocesses handle --trace-startup by themselves to begin
+  // trace as early as possible. Don't start twice, otherwise the trace
+  // buffer can't be correctly flushed on the end of startup tracing.
+  if (!tracing_startup || !TraceLog::GetInstance()->IsEnabled()) {
+    TraceLog::GetInstance()->SetEnabled(
+        base::debug::CategoryFilter(category_filter_str),
+        static_cast<base::debug::TraceLog::Options>(options));
+  }
 }
 
 void ChildTraceMessageFilter::OnEndTracing() {
diff --git a/components/tracing/child_trace_message_filter.h b/components/tracing/child_trace_message_filter.h
index cbd300f..8fe301a 100644
--- a/components/tracing/child_trace_message_filter.h
+++ b/components/tracing/child_trace_message_filter.h
@@ -32,7 +32,8 @@ class ChildTraceMessageFilter : public IPC::ChannelProxy::MessageFilter {
   // Message handlers.
   void OnBeginTracing(const std::string& category_filter_str,
                       base::TimeTicks browser_time,
-                      int options);
+                      int options,
+                      bool tracing_startup);
   void OnEndTracing();
   void OnEnableMonitoring(const std::string& category_filter_str,
                           base::TimeTicks browser_time,
diff --git a/components/tracing/tracing_messages.h b/components/tracing/tracing_messages.h
index 25b45bd..2b491ba 100644
--- a/components/tracing/tracing_messages.h
+++ b/components/tracing/tracing_messages.h
@@ -16,10 +16,11 @@
 #define IPC_MESSAGE_START TracingMsgStart
 
 // Sent to all child processes to enable trace event recording.
-IPC_MESSAGE_CONTROL3(TracingMsg_BeginTracing,
+IPC_MESSAGE_CONTROL4(TracingMsg_BeginTracing,
                      std::string /*  category_filter_str */,
                      base::TimeTicks /* browser_time */,
-                     int /* base::debug::TraceLog::Options */)
+                     int /* base::debug::TraceLog::Options */,
+                     bool /* tracing_startup */)
 
 // Sent to all child processes to disable trace event recording.
 IPC_MESSAGE_CONTROL0(TracingMsg_EndTracing)