Change sync conflict resolution for extensions

sync/engine/conflict_resolver.cc

Index: sync/engine/conflict_resolver.cc
diff --git a/sync/engine/conflict_resolver.cc b/sync/engine/conflict_resolver.cc
index 0af30977c331e8840fe7ef27a77362114de875af..f1f15914152f2d631122324a50d0f34f1d1eb941 100644
--- a/sync/engine/conflict_resolver.cc
+++ b/sync/engine/conflict_resolver.cc
@@ -115,8 +115,11 @@ void ConflictResolver::ProcessSimpleConflict(WriteTransaction* trans,
   //    safely ignore the server changes as redundant.
   // f) Otherwise, it's in general safer to ignore local changes, with the
   //    exception of deletion conflicts (choose to undelete) and conflicts
-  //    where the non_unique_name or parent don't match.
-  if (!entry.GetServerIsDel()) {
+  //    where the non_unique_name or parent don't match. Another exception is

[Nicolas Zea, 2016/02/11 23:41:50]

nit: may as well put this into its own e) bullet

[asargent_no_longer_on_chrome, 2016/02/18 00:53:45]

Done.

+  //    the case of extensions and apps, where we want uninstalls to win over
+  //    local modifications to avoid "back from the dead" reinstalls.
+  ModelType type = entry.GetModelType();
+  if (!entry.GetServerIsDel() || (type == EXTENSIONS || type == APPS)) {
     // TODO(nick): The current logic is arbitrary; instead, it ought to be made
     // consistent with the ModelAssociator behavior for a datatype.  It would
     // be nice if we could route this back to ModelAssociator code to pick one