Delete some unused code found by -Wunused-function

chrome/browser/ui/cocoa/extensions/extension_action_context_menu.mm

Index: chrome/browser/ui/cocoa/extensions/extension_action_context_menu.mm
diff --git a/chrome/browser/ui/cocoa/extensions/extension_action_context_menu.mm b/chrome/browser/ui/cocoa/extensions/extension_action_context_menu.mm
index d48e287bec6d66ea2aee817598112026b993233a..4ad0c596e5bb456112de2165284e1458ee5c0e80 100644
--- a/chrome/browser/ui/cocoa/extensions/extension_action_context_menu.mm
+++ b/chrome/browser/ui/cocoa/extensions/extension_action_context_menu.mm
@@ -96,16 +96,6 @@ enum {
   kExtensionContextManage = 7,
 };
 
-int CurrentTabId() {
-  Browser* browser = browser::GetLastActiveBrowser();
-  if(!browser)
-    return -1;
-  WebContents* contents = chrome::GetActiveWebContents(browser);
-  if (!contents)
-    return -1;
-  return ExtensionTabUtil::GetTabId(contents);
-}
-
 }  // namespace
 
 - (id)initWithExtension:(const Extension*)extension