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

content/renderer/devtools/devtools_agent.h

Index: content/renderer/devtools/devtools_agent.h
diff --git a/content/renderer/devtools/devtools_agent.h b/content/renderer/devtools/devtools_agent.h
index d5d36e547e51079e3f9e6facb45a3b54af709f2e..bc0c5788c6ae386a0366ad50c8cdba2ef3018fa3 100644
--- a/content/renderer/devtools/devtools_agent.h
+++ b/content/renderer/devtools/devtools_agent.h
@@ -9,6 +9,7 @@
 
 #include "base/macros.h"
 #include "base/memory/scoped_ptr.h"
+#include "base/trace_event/trace_config.h"
 #include "content/common/content_export.h"
 #include "content/public/common/console_message_level.h"
 #include "content/public/renderer/render_frame_observer.h"
@@ -53,6 +54,9 @@ class CONTENT_EXPORT DevToolsAgent
  private:
   friend class DevToolsAgentTest;
 
+  void enableTracingWithTraceConfig(
+      const base::trace_event::TraceConfig& trace_config);
+
   // RenderFrameObserver implementation.
   bool OnMessageReceived(const IPC::Message& message) override;
   void WidgetWillClose() override;
@@ -69,6 +73,8 @@ class CONTENT_EXPORT DevToolsAgent
 
   bool requestDevToolsForFrame(blink::WebLocalFrame* frame) override;
 
+  void enableTracingWithConfigStr(
+      const blink::WebString& devtools_style_config) override;
   void enableTracing(const blink::WebString& category_filter) override;
   void disableTracing() override;