[SyncFS] Initialize SyncEngine::remote_change_processor_ in the constructor

This should fix a memory error spotted by:
http://build.chromium.org/p/chromium.memory.fyi/builders/Linux%20Tests%20%28valgrind%29%285%29/builds/28092/steps/memory%20test%3A%20unit/logs/8E6AD1C2FCE494CD

BUG=347425, 380615
NOTRY=true
TBR=peria@chromium.org

Review URL: https://codereview.chromium.org/326933002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@276000 0039d316-1c4b-4281-b951-d872f2087c98

chrome/browser/sync_file_system/drive_backend/sync_engine.cc

@@ -580,6 +580,7 @@ SyncEngine::SyncEngine(
       signin_manager_(signin_manager),
       token_service_(token_service),
       request_context_(request_context),
+      remote_change_processor_(NULL),
       service_state_(REMOTE_SERVICE_TEMPORARY_UNAVAILABLE),
       sync_enabled_(false),
       env_override_(env_override),