Use FrameTreeNode ID as frameId in extension APIs

chrome/browser/extensions/api/web_navigation/web_navigation_api_helpers.cc

Index: chrome/browser/extensions/api/web_navigation/web_navigation_api_helpers.cc
diff --git a/chrome/browser/extensions/api/web_navigation/web_navigation_api_helpers.cc b/chrome/browser/extensions/api/web_navigation/web_navigation_api_helpers.cc
index 3b04125a35373f2826840b85c5a3914624cbc65d..0b274157cb92161598d15afdfbf624552e590aa0 100644
--- a/chrome/browser/extensions/api/web_navigation/web_navigation_api_helpers.cc
+++ b/chrome/browser/extensions/api/web_navigation/web_navigation_api_helpers.cc
@@ -62,13 +62,10 @@ void DispatchEvent(content::BrowserContext* browser_context,
 int GetFrameId(content::RenderFrameHost* frame_host) {
   if (!frame_host)
     return -1;
-  return !frame_host->GetParent() ? 0 : frame_host->GetRoutingID();
+  return !frame_host->GetParent() ? 0 : frame_host->GetFrameTreeNodeID();
 }
 
 // Constructs and dispatches an onBeforeNavigate event.
-// TODO(dcheng): Is the parent process ID needed here? http://crbug.com/393640
-// Collisions are probably possible... but maybe this won't ever happen because
-// of the SiteInstance grouping policies.
 void DispatchOnBeforeNavigate(content::WebContents* web_contents,
                               content::RenderFrameHost* frame_host,
                               const GURL& validated_url) {