Allow enabling tracing in base without an instance of the tracing controller

sky/shell/platform/mac/platform_mac.mm

@@ -12,11 +12,11 @@
 #include "base/logging.h"
 #include "base/mac/scoped_nsautorelease_pool.h"
 #include "base/message_loop/message_loop.h"
-#include "base/trace_event/trace_event.h"
 #include "mojo/edk/embedder/embedder.h"
 #include "mojo/edk/embedder/simple_platform_support.h"
 #include "sky/shell/shell.h"
 #include "sky/shell/switches.h"
+#include "sky/shell/tracing_controller.h"
 #include "sky/shell/ui_delegate.h"
 #include "ui/gl/gl_surface.h"
 
@@ -60,12 +60,9 @@ int PlatformMacMain(int argc,
     // Usually, all tracing within flutter is managed via the tracing controller
     // The tracing controller is accessed via the shell instance. This means
     // that tracing can only be enabled once that instance is created. Traces
-    // early in startup are lost. This enables tracing in base manually till
-    // the tracing controller takes over.
-    base::trace_event::TraceLog::GetInstance()->SetEnabled(
-        base::trace_event::TraceConfig("*",
-                                       base::trace_event::RECORD_UNTIL_FULL),
-        base::trace_event::TraceLog::RECORDING_MODE);
+    // early in startup are lost. This enables tracing only in base manually
+    // till the tracing controller takes over.
+    sky::shell::TracingController::StartBaseTracing();
   }
 
   scoped_ptr<base::MessageLoopForUI> message_loop(new base::MessageLoopForUI());

sky/shell/tracing_controller.h

@@ -28,6 +28,12 @@ class TracingController {
   void StopTracing(const base::FilePath& path,
                    bool terminateLoopWhenDone = false);
 
+  // Enables tracing in base. Only use this if an instance of a tracing
+  // controller cannot be obtained (can happen early in the lifecycle of the
+  // process). In most cases, the |StartTracing| method on an instance of the
+  // tracing controller should be used.
+  static void StartBaseTracing();
+
   base::FilePath PictureTracingPathForCurrentTime() const;
   
   base::FilePath PictureTracingPathForCurrentTime(base::FilePath dir) const;
@@ -57,7 +63,6 @@ class TracingController {
   bool tracing_active_;
 
   void StartDartTracing();
-  void StartBaseTracing();
   void StopDartTracing();
   void StopBaseTracing();
   void FinalizeTraceFile();