[Sync] Convert SyncSessionSnapshot to a copy-able class.

sync/engine/sync_engine_event.cc

Index: sync/engine/sync_engine_event.cc
diff --git a/sync/engine/syncer_types.cc b/sync/engine/sync_engine_event.cc
similarity index 73%
rename from sync/engine/syncer_types.cc
rename to sync/engine/sync_engine_event.cc
index 18994668559280bfb4460c3d125a34af43fcf290..9ffb281414b6db3d6a7e57b8ccd9c2852014a20d 100644
--- a/sync/engine/syncer_types.cc
+++ b/sync/engine/sync_engine_event.cc
@@ -2,12 +2,11 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "sync/engine/syncer_types.h"
+#include "sync/engine/sync_engine_event.h"
 
 namespace browser_sync {
 
-SyncEngineEvent::SyncEngineEvent(EventCause cause) : what_happened(cause),
-                                                     snapshot(NULL) {
+SyncEngineEvent::SyncEngineEvent(EventCause cause) : what_happened(cause) {
 }
 
 SyncEngineEvent::~SyncEngineEvent() {}