Add function to register a synthetic trial with the trial hash.

chrome/browser/metrics/metrics_service_accessor.h

Index: chrome/browser/metrics/metrics_service_accessor.h
===================================================================
--- chrome/browser/metrics/metrics_service_accessor.h	(revision 287334)
+++ chrome/browser/metrics/metrics_service_accessor.h	(working copy)
@@ -5,6 +5,7 @@
 #ifndef CHROME_BROWSER_METRICS_METRICS_SERVICE_ACCESSOR_H_
 #define CHROME_BROWSER_METRICS_METRICS_SERVICE_ACCESSOR_H_
 
+#include <stdint.h>
 #include <string>
 
 #include "base/macros.h"
@@ -34,8 +35,8 @@
   // is registered for a given trial name will be recorded. The values passed
   // in must not correspond to any real field trial in the code.

[jwd, 2014/08/05 19:26:05]

Update comment.

[Alexei Svitkine (slow), 2014/08/05 19:31:40]

Done. Gutted most of the comment, instead pointing to the equivalent comment on
the MetricsService method.

   static bool RegisterSyntheticFieldTrial(MetricsService* metrics_service,
-                                          const std::string& trial,
-                                          const std::string& group);
+                                          uint32_t trial_name_hash,
+                                          uint32_t group_name_hash);
 
  private:
   DISALLOW_COPY_AND_ASSIGN(MetricsServiceAccessor);