[Sync] Rip out overly-complicated ExtensionData class

chrome/browser/extensions/extension_sync_data.h

Index: chrome/browser/extensions/extension_sync_data.h
diff --git a/chrome/browser/extensions/extension_sync_data.h b/chrome/browser/extensions/extension_sync_data.h
index c454946d08bf218c81e0570848894305a13cf5da..312103d6f9a394bb0f93b4cb6f733b9556aac074 100644
--- a/chrome/browser/extensions/extension_sync_data.h
+++ b/chrome/browser/extensions/extension_sync_data.h
@@ -16,6 +16,12 @@ struct ExtensionSyncData {
   ExtensionSyncData();
   ~ExtensionSyncData();
 
+  // Merge |new_data| into this object.  All version-independent
+  // properties are copied from |new_data|, and version-dependent
+  // properties are copied only if |new_data|'s version is equal to or
+  // greater than the current version.
+  void Merge(const ExtensionSyncData& new_data);
+
   std::string id;
 
   // Version-independent properties (i.e., used even when the
@@ -29,7 +35,6 @@ struct ExtensionSyncData {
   // version of the currenty-installed extension matches |version|).
   Version version;
   GURL update_url;
-
   // Used only for debugging.
   std::string name;
 };