Do not suppress HTTP Authenticaiton in WebController.

ios/chrome/browser/tabs/tab.h

Index: ios/chrome/browser/tabs/tab.h
diff --git a/ios/chrome/browser/tabs/tab.h b/ios/chrome/browser/tabs/tab.h
index 13a84a74ae97722112d08cae8e0bd04a46faa695..93e3621894ad513371d3b597485fe3459619822d 100644
--- a/ios/chrome/browser/tabs/tab.h
+++ b/ios/chrome/browser/tabs/tab.h
@@ -349,6 +349,10 @@ extern NSString* const kProxyPassthroughHeaderValue;
 // Evaluates U2F result.
 - (void)evaluateU2FResultFromURL:(const GURL&)url;
 
+// Cancels prerendering. Can be called only for prerender tabs (where

[marq (ping after 24h), 2017/03/27 13:00:13]

Can you clarify how the 'can only be called for prerender tabs' contract is
enforced?

[Eugene But (OOO till 7-30), 2017/03/27 16:46:50]

It is enforced via DCHECK like in other invariant in Chrome code. Is this
something that you want me to document in the comments? For me this seems pretty
standard way to enforce the contracts.

[marq (ping after 24h), 2017/03/27 17:04:30]

I was mostly looking for a clearer statement in the comment -- "It is an error
to call this on anything except a prerender tab" as opposed to (say) "Calling
this on a non-prerender tab does nothing".

[Eugene But (OOO till 7-30), 2017/03/27 17:19:07]

Thanks for clarification. Done.

+// |isPrerenderTab| is set to YES).
+- (void)discardPrerender;
+
 @end
 
 #endif  // IOS_CHROME_BROWSER_TABS_TAB_H_