Implement request mobile site.

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 ddc417fb6f0a1c3c6c5fdf8bc801d57196a69fb9..92e5abf1448775df61b5560a5f3c16b437c75fa4 100644
--- a/ios/chrome/browser/tabs/tab.h
+++ b/ios/chrome/browser/tabs/tab.h
@@ -12,6 +12,7 @@
 
 #import "components/signin/ios/browser/manage_accounts_delegate.h"
 #include "ios/net/request_tracker.h"
+#include "ios/web/public/user_agent.h"
 #import "ios/web/public/web_state/ui/crw_web_delegate.h"
 #include "ui/base/page_transition_types.h"
 
@@ -238,9 +239,10 @@ extern NSString* const kProxyPassthroughHeaderValue;
 // current content.
 - (void)switchToReaderMode;
 
-// Remove the UIWebView and reload the current url.  Used by request desktop
-// so the updated user agent is used.
-- (void)reloadForDesktopUserAgent;
+// Removes the web view and loads the original url of the last non-redirect item

[kkhorimoto, 2017/04/11 01:09:41]

We aren't removing the web view anymore, are we?  Can't we just set the
|customUserAgent| property of the WKWebView?

[Eugene But (OOO till 7-30), 2017/04/11 02:11:56]

In any case Tab should not make any assumptions about implementation details or
even that WKWebView is used.

[liaoyuke, 2017/04/11 18:27:20]

That is a very good point! Thanks!

[liaoyuke, 2017/04/11 18:27:20]

Set |customUserAgent| property requires re-factoring a few files to use
UserAgentType, so I wanted to save it to a separate CL.

+// (including non-history items).  Used by request desktop/mobile site so the
+// updated user agent is used.
+- (void)reloadWithUserAgentType:(web::UserAgentType)userAgentType;
 
 // Ensures the toolbar visibility matches |visible|.
 - (void)updateFullscreenWithToolbarVisible:(BOOL)visible;