Timeline: produce session cookie when timeline is started

Source/core/inspector/InspectorTimelineAgent.cpp

Index: Source/core/inspector/InspectorTimelineAgent.cpp
diff --git a/Source/core/inspector/InspectorTimelineAgent.cpp b/Source/core/inspector/InspectorTimelineAgent.cpp
index 08c88721f1402ae30bf78ca011d3a2525798eaa5..c901add66c37fe076d73a236d36242c74318dd24 100644
--- a/Source/core/inspector/InspectorTimelineAgent.cpp
+++ b/Source/core/inspector/InspectorTimelineAgent.cpp
@@ -73,6 +73,7 @@ static const char includeCounters[] = "includeCounters";
 static const char includeGPUEvents[] = "includeGPUEvents";
 static const char bufferEvents[] = "bufferEvents";
 static const char liveEvents[] = "liveEvents";
+static const char sessionId[] = "sessionId";
 static const char traceEventCategoryFilter[] = "traceEventCategoryFilter";
 }
 
@@ -341,10 +342,11 @@ void InspectorTimelineAgent::start(ErrorString* errorString, const int* maxCallS
     m_state->setBoolean(TimelineAgentState::includeGPUEvents, includeGPUEvents && *includeGPUEvents);
     m_state->setBoolean(TimelineAgentState::bufferEvents, bufferEvents && *bufferEvents);
     m_state->setString(TimelineAgentState::liveEvents, liveEvents ? *liveEvents : "");
+    initializeSessionId();
 
     innerStart();
     bool fromConsole = false;
-    m_frontend->started(&fromConsole);
+    m_frontend->started(sessionId(), &fromConsole);
 }
 
 bool InspectorTimelineAgent::isStarted()
@@ -366,6 +368,10 @@ void InspectorTimelineAgent::innerStart()
     }
     m_instrumentingAgents->setInspectorTimelineAgent(this);
     ScriptGCEvent::addEventListener(this);
+    TRACE_EVENT_INSTANT1(TRACE_DISABLED_BY_DEFAULT("devtools.timeline"), "TimelineStarted", "sessionId", sessionId().utf8());
+    if (m_layerTreeId) {
+        TRACE_EVENT_INSTANT2(TRACE_DISABLED_BY_DEFAULT("devtools.timeline"), "SetLayerTreeId", "sessionId", sessionId().utf8(), "layerTreeId", m_layerTreeId);
+    }
     if (m_client) {
         TraceEventDispatcher* dispatcher = TraceEventDispatcher::instance();
         dispatcher->addListener(InstrumentationEvents::BeginFrame, TRACE_EVENT_PHASE_INSTANT, this, &InspectorTimelineAgent::onBeginImplSideFrame, m_client);
@@ -398,6 +404,7 @@ void InspectorTimelineAgent::stop(ErrorString* errorString, RefPtr<TypeBuilder::
     m_state->setBoolean(TimelineAgentState::startedFromProtocol, false);
     m_state->setBoolean(TimelineAgentState::bufferEvents, false);
     m_state->setString(TimelineAgentState::liveEvents, "");
+    m_state->setString(TimelineAgentState::sessionId, "");
 
     if (!isStarted()) {
         *errorString = "Timeline was not started";
@@ -446,6 +453,24 @@ void InspectorTimelineAgent::innerStop(bool fromConsole)
         m_overlay->finishedRecordingProfile();
 }
 
+String InspectorTimelineAgent::sessionId() const
+{
+    return m_state->getString(TimelineAgentState::sessionId);
+}
+
+void InspectorTimelineAgent::initializeSessionId()
+{
+    static unsigned lastTimelineSessionId;
+    String sessionId = IdentifiersFactory::createIdentifier();
+    m_state->setString(TimelineAgentState::sessionId, sessionId);
+}
+
+void InspectorTimelineAgent::setLayerTreeId(int layerTreeId)
+{
+    m_layerTreeId = layerTreeId;
+    TRACE_EVENT_INSTANT2(TRACE_DISABLED_BY_DEFAULT("devtools.timeline"), "setLayerTreeId", "sessionId", sessionId().utf8(), "layerTreeId", m_layerTreeId);
+}
+
 void InspectorTimelineAgent::didBeginFrame(int frameId)
 {
     TraceEventDispatcher::instance()->processBackgroundEvents();
@@ -830,9 +855,10 @@ void InspectorTimelineAgent::consoleTimeline(ExecutionContext* context, const St
     mainFrame()->console().addMessage(ConsoleAPIMessageSource, DebugMessageLevel, message, String(), 0, 0, nullptr, state);
     m_consoleTimelines.append(title);
     if (!isStarted()) {
+        initializeSessionId();
         innerStart();
         bool fromConsole = true;
-        m_frontend->started(&fromConsole);
+        m_frontend->started(sessionId(), &fromConsole);
     }
     appendRecord(TimelineRecordFactory::createTimeStampData(message), TimelineRecordType::TimeStamp, true, frameForExecutionContext(context));
 }