Update DevTools Tracing.Start to accept trace config as a parameter

third_party/WebKit/Source/core/inspector/InspectorTracingAgent.cpp

Index: third_party/WebKit/Source/core/inspector/InspectorTracingAgent.cpp
diff --git a/third_party/WebKit/Source/core/inspector/InspectorTracingAgent.cpp b/third_party/WebKit/Source/core/inspector/InspectorTracingAgent.cpp
index 6d6a25cef00561a7bb4cec5c445b66f2edf666f4..b2de376aff37bd5c31155b236cdf2abefccb910b 100644
--- a/third_party/WebKit/Source/core/inspector/InspectorTracingAgent.cpp
+++ b/third_party/WebKit/Source/core/inspector/InspectorTracingAgent.cpp
@@ -43,14 +43,21 @@ void InspectorTracingAgent::restore()
 {
     emitMetadataEvents();
 }
-void InspectorTracingAgent::start(ErrorString*,
+void InspectorTracingAgent::start(ErrorString* errorString,
     const Maybe<String>& categories,
     const Maybe<String>& options,
     const Maybe<double>& bufferUsageReportingInterval,
     const Maybe<String>& transferMode,
+    const Maybe<protocol::Tracing::TraceConfig>& config,
     PassOwnPtr<StartCallback> callback)
 {
     ASSERT(sessionId().isEmpty());
+    if (config.isJust()) {
+        *errorString =
+            "Using trace config on renderer targets is not supported yet.";
+        return;
+    }
+
     m_state->setString(TracingAgentState::sessionId, IdentifiersFactory::createIdentifier());
     m_client->enableTracing(categories.fromMaybe(String()));
     emitMetadataEvents();