Add UMA metrics and histograms for locally managed users.

chrome/common/extensions/extension.cc

Index: chrome/common/extensions/extension.cc
===================================================================
--- chrome/common/extensions/extension.cc	(revision 177135)
+++ chrome/common/extensions/extension.cc	(working copy)
@@ -1329,6 +1329,10 @@
   return manifest()->is_theme();
 }
 
+bool Extension::is_content_pack() const {
+  return manifest()->HasKey(keys::kContentPack);
+}
+
 ExtensionResource Extension::GetContentPackSiteList() const {
   if (content_pack_site_list_.empty())
     return ExtensionResource();