Add a mode flag to the tracing framework.

content/browser/devtools/devtools_tracing_handler.h

Index: content/browser/devtools/devtools_tracing_handler.h
diff --git a/content/browser/devtools/devtools_tracing_handler.h b/content/browser/devtools/devtools_tracing_handler.h
index 2d9ed52fd591c79962facc47e2f49487c52d701a..86ddf00aa59d79f27e7e8cb8dae51d7b6caaa3f6 100644
--- a/content/browser/devtools/devtools_tracing_handler.h
+++ b/content/browser/devtools/devtools_tracing_handler.h
@@ -5,6 +5,7 @@
 #ifndef CONTENT_BROWSER_DEVTOOLS_DEVTOOLS_TRACING_HANDLER_H_
 #define CONTENT_BROWSER_DEVTOOLS_DEVTOOLS_TRACING_HANDLER_H_
 
+#include "base/debug/trace_event.h"
 #include "content/browser/devtools/devtools_protocol.h"
 #include "content/public/browser/trace_subscriber.h"
 
@@ -34,6 +35,9 @@ class DevToolsTracingHandler
   scoped_ptr<DevToolsProtocol::Response> OnEnd(
       DevToolsProtocol::Command* command);
 
+  base::debug::TraceLog::Options TraceOptionsFromString(
+      const std::string& options);
+
   bool is_running_;
 
   DISALLOW_COPY_AND_ASSIGN(DevToolsTracingHandler);