[Sync] Move sync/{internal_api,syncable} into syncer namespace

sync/engine/conflict_resolver.h

Index: sync/engine/conflict_resolver.h
diff --git a/sync/engine/conflict_resolver.h b/sync/engine/conflict_resolver.h
index 733348ce9a3310b03855afa4a315969344240991..e0fce1d8ce2d978153ea036d4e6fafd7e643cf5c 100644
--- a/sync/engine/conflict_resolver.h
+++ b/sync/engine/conflict_resolver.h
@@ -17,6 +17,8 @@
 #include "base/gtest_prod_util.h"
 #include "sync/engine/syncer_types.h"
 
+namespace syncer {
+
 namespace syncable {
 class BaseTransaction;
 class Id;
@@ -24,8 +26,6 @@ class MutableEntry;
 class WriteTransaction;
 }  // namespace syncable
 
-namespace syncer {
-
 class Cryptographer;
 
 namespace sessions {