Add base:: to fix the build

TEST=it compiles
BUG=none
Review URL: http://codereview.chromium.org/6360010

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@72109 0039d316-1c4b-4281-b951-d872f2087c98

chrome/browser/enumerate_modules_model_win.cc

@@ -817,7 +817,7 @@ EnumerateModulesModel::EnumerateModulesModel()
         this, &EnumerateModulesModel::ScanNow);
   }
 
-  lock = new Lock();
+  lock = new base::Lock();
 }
 
 EnumerateModulesModel::~EnumerateModulesModel() {