Merge pull request #2140 from chinmaygarde/master

Start tracing in base before a tracing controller instance is available

sky/shell/platform/mac/platform_mac.mm

@@ -15,6 +15,8 @@
 #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"
 
@@ -53,6 +55,16 @@ int PlatformMacMain(int argc,
 
   InitializeLogging();
 
+  base::CommandLine& command_line = *base::CommandLine::ForCurrentProcess();
+  if (command_line.HasSwitch(sky::shell::switches::kTraceStartup)) {
+    // 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 only in base manually
+    // till the tracing controller takes over.
+    sky::shell::TracingController::StartBaseTracing();
+  }
+
   scoped_ptr<base::MessageLoopForUI> message_loop(new base::MessageLoopForUI());
 
 #if TARGET_OS_IPHONE

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();