[Sync] Put everything in sync/api into csync namespace

sync/api/sync_change.h

Index: sync/api/sync_change.h
diff --git a/sync/api/sync_change.h b/sync/api/sync_change.h
index 19218f56d19385f95c009c6b354cc904a8ba493d..11dea71c6409df3226dbb1941d98f4a575349b64 100644
--- a/sync/api/sync_change.h
+++ b/sync/api/sync_change.h
@@ -12,6 +12,8 @@
 
 #include "sync/api/sync_data.h"
 
+namespace csync {
+
 // A SyncChange object reflects a change to a piece of synced data. The change
 // can be either a delete, add, or an update. All data relevant to the change
 // is encapsulated within the SyncChange, which, once created, is immutable.
@@ -64,4 +66,6 @@ class SyncChange {
 // gmock printer helper.
 void PrintTo(const SyncChange& sync_change, std::ostream* os);
 
+}  // namespace csync
+
 #endif  // SYNC_API_SYNC_CHANGE_H_