Add UMA data for memory pressure warning received for sync

chrome/browser/sync/profile_sync_service.h

Index: chrome/browser/sync/profile_sync_service.h
diff --git a/chrome/browser/sync/profile_sync_service.h b/chrome/browser/sync/profile_sync_service.h
index 1ad2cb76e87988752835fe9bb76c4cd7d0b29a60..9f047cae2d0bf7d1b6985fda2414fd151892d923 100644
--- a/chrome/browser/sync/profile_sync_service.h
+++ b/chrome/browser/sync/profile_sync_service.h
@@ -14,6 +14,7 @@
 #include "base/files/file_path.h"
 #include "base/gtest_prod_util.h"
 #include "base/location.h"
+#include "base/memory/memory_pressure_listener.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/scoped_vector.h"
 #include "base/memory/weak_ptr.h"
@@ -891,6 +892,13 @@ class ProfileSyncService : public sync_driver::SyncService,
   // Tell the sync server that this client has disabled sync.
   void RemoveClientFromServer() const;
 
+  // Called when the system is under memory pressure.
+  void OnMemoryPressure(
+      base::MemoryPressureListener::MemoryPressureLevel memory_pressure_level);
+
+  // Check if previous shutdown is crash or not.

[stanisc, 2015/05/15 20:31:04]

If there was a crash that means there wasn't a clean shutdown.
So perhaps rephrase this a bit to make it clearer.
Also explain result of the function. It returns void. Does it have any side
effect?

[Gang Wu, 2015/05/15 21:13:46]

Done.

+  void CheckPreviousShutdownMemoryWarning();
+
   // Factory used to create various dependent objects.
   scoped_ptr<ProfileSyncComponentsFactory> factory_;
 
@@ -1070,6 +1078,9 @@ class ProfileSyncService : public sync_driver::SyncService,
 
   scoped_ptr<browser_sync::SyncStoppedReporter> sync_stopped_reporter_;
 
+  // Listens for the system being under memory pressure.
+  scoped_ptr<base::MemoryPressureListener> memory_pressure_listener_;
+
   base::WeakPtrFactory<ProfileSyncService> weak_factory_;
 
   // We don't use |weak_factory_| for the StartupController because the weak