Add histogram to track Mojo shell / renderer connection init

content/renderer/renderer_main.cc

Index: content/renderer/renderer_main.cc
diff --git a/content/renderer/renderer_main.cc b/content/renderer/renderer_main.cc
index b5bf9ae0a51755d8b816994e91fd48eaac7b326d..70501f90eac37acd889ffcdf43cd16e5736f4bc1 100644
--- a/content/renderer/renderer_main.cc
+++ b/content/renderer/renderer_main.cc
@@ -14,11 +14,13 @@
 #include "base/message_loop/message_loop.h"
 #include "base/metrics/field_trial.h"
 #include "base/metrics/histogram.h"

[Ilya Sherman, 2016/03/07 22:08:32]

nit: Do you need both the histogram and the histogram_macros includes?

[Ken Rockot(use gerrit already), 2016/03/07 22:24:50]

Doubtful - I've removed histogram.h

+#include "base/metrics/histogram_macros.h"
 #include "base/metrics/statistics_recorder.h"
 #include "base/pending_task.h"
 #include "base/strings/string_util.h"
 #include "base/sys_info.h"
 #include "base/threading/platform_thread.h"
+#include "base/timer/elapsed_timer.h"
 #include "base/timer/hi_res_timer_manager.h"
 #include "base/trace_event/trace_event.h"
 #include "build/build_config.h"
@@ -93,7 +95,12 @@ int RendererMain(const MainFunctionParams& parameters) {
 
   const base::CommandLine& parsed_command_line = parameters.command_line;
 
-  MojoShellConnectionImpl::Create();
+  {
+    base::ElapsedTimer timer;
+    MojoShellConnectionImpl::Create();
+    LOCAL_HISTOGRAM_TIMES("Mojo.Shell.RenderProcessInitializationTime",
+                          timer.Elapsed());

[Ilya Sherman, 2016/03/07 22:08:32]

Are you sure you want a *local* histogram, i.e. one that is not uploaded to UMA?
 What's the expected use for this data?

[Ken Rockot(use gerrit already), 2016/03/07 22:24:50]

No! Good catch, I wanted an UMA histogram. Fixed.

+  }
 
 #if defined(OS_MACOSX)
   base::mac::ScopedNSAutoreleasePool* pool = parameters.autorelease_pool;