[DevTools] Add implementation for Tracing.start with optional parameters.

content/browser/devtools/protocol/tracing_handler.h

Index: content/browser/devtools/protocol/tracing_handler.h
diff --git a/content/browser/devtools/protocol/tracing_handler.h b/content/browser/devtools/protocol/tracing_handler.h
index d2fc77307b92cd2fa0238089ca170c9c8b3d70a8..c629188b73d77df6eda9035f09b0265707cb320c 100644
--- a/content/browser/devtools/protocol/tracing_handler.h
+++ b/content/browser/devtools/protocol/tracing_handler.h
@@ -20,18 +20,17 @@ class TracingHandler {
 
   void SetClient(scoped_ptr<Client> client);
 
-  // TODO(dgozman): remove sync version after migration.
-  Response Start(const std::string& categories,
-                 const std::string& options,
-                 const double* buffer_usage_reporting_interval);
   scoped_refptr<DevToolsProtocol::Response> Start(
       const std::string& categories,
       const std::string& options,
       const double* buffer_usage_reporting_interval,
       scoped_refptr<DevToolsProtocol::Command> command);
+  scoped_refptr<DevToolsProtocol::Response> Start(
+      const std::string* categories,
+      const std::string* options,
+      const double* buffer_usage_reporting_interval,
+      scoped_refptr<DevToolsProtocol::Command> command);
 
-  // TODO(dgozman): remove sync version after migration.
-  Response End();
   scoped_refptr<DevToolsProtocol::Response> End(
       scoped_refptr<DevToolsProtocol::Command> command);