Support saving browser metrics to disk and reading them during next run.

content/browser/browser_main_runner.cc

Index: content/browser/browser_main_runner.cc
diff --git a/content/browser/browser_main_runner.cc b/content/browser/browser_main_runner.cc
index 96a3454f1499edbb0211afbcdb1ba8024cb6e2bc..085a546a4e486f870b244025459cecbb98264518 100644
--- a/content/browser/browser_main_runner.cc
+++ b/content/browser/browser_main_runner.cc
@@ -11,6 +11,7 @@
 #include "base/macros.h"
 #include "base/metrics/histogram.h"
 #include "base/metrics/histogram_macros.h"
+#include "base/metrics/persistent_histogram_allocator.h"
 #include "base/metrics/statistics_recorder.h"
 #include "base/profiler/scoped_profile.h"
 #include "base/profiler/scoped_tracker.h"
@@ -224,6 +225,13 @@ class BrowserMainRunnerImpl : public BrowserMainRunner {
 
       notification_service_.reset(NULL);
 
+      // Dump all the persistent metrics to a file for upload during the next
+      // run of the browser.
+      base::GlobalHistogramAllocator* allocator =
+          base::GlobalHistogramAllocator::Get();
+      if (allocator)
+        allocator->WritePersistentLocation();
+
       is_shutdown_ = true;
     }
   }