Add a do_not_sync pref to ExtensionPrefs.

chrome/browser/extensions/extension_sync_bundle.cc

Index: chrome/browser/extensions/extension_sync_bundle.cc
diff --git a/chrome/browser/extensions/extension_sync_bundle.cc b/chrome/browser/extensions/extension_sync_bundle.cc
index facac2295cb7f596b2f08341f261883489af5a91..2333ffa6b94f430147f535194a32077f68168b2f 100644
--- a/chrome/browser/extensions/extension_sync_bundle.cc
+++ b/chrome/browser/extensions/extension_sync_bundle.cc
@@ -6,6 +6,8 @@
 
 #include "base/location.h"
 #include "chrome/browser/extensions/extension_sync_service.h"
+#include "chrome/browser/extensions/extension_util.h"
+#include "chrome/browser/profiles/profile.h"
 #include "chrome/common/extensions/sync_helper.h"
 #include "extensions/common/extension.h"
 #include "extensions/common/extension_set.h"
@@ -142,13 +144,15 @@ std::vector<ExtensionSyncData> ExtensionSyncBundle::GetPendingData() const {
 void ExtensionSyncBundle::GetExtensionSyncDataListHelper(
     const ExtensionSet& extensions,
     std::vector<ExtensionSyncData>* sync_data_list) const {
+  Profile* profile = extension_sync_service_->profile();
+
   for (ExtensionSet::const_iterator it = extensions.begin();
        it != extensions.end(); ++it) {
     const Extension& extension = *it->get();
     // If we have pending extension data for this extension, then this
     // version is out of date.  We'll sync back the version we got from
     // sync.
-    if (IsSyncing() && sync_helper::IsSyncableExtension(&extension) &&
+    if (IsSyncing() && util::ShouldSyncExtension(&extension, profile) &&

[not at google - send to devlin, 2014/06/13 20:01:22]

could you add a comment to sync_helper.h saying "you probably want to use
util::ShoudSyncExtension not these methods".

[xiyuan, 2014/06/13 20:35:42]

Done.

         !HasPendingExtensionId(extension.id())) {
       sync_data_list->push_back(
           extension_sync_service_->GetExtensionSyncData(extension));