Revert of Fixes document type detection on iOS 9.

ios/web/web_state/ui/crw_wk_web_view_web_controller.mm

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #import "ios/web/web_state/ui/crw_wk_web_view_web_controller.h"
 
 #import <WebKit/WebKit.h>
 
 #include "base/containers/mru_cache.h"
 #include "base/ios/ios_util.h"
@@ skipping 518 matching lines @@
 // to |WEB_VIEW_DOCUMENT| because it does not support iframe creation used
 // by core.js to communicate back. That functionality is only supported
 // by |WEB_VIEW_HTML_DOCUMENT|. |WEB_VIEW_DOCUMENT| is used when displaying
 // non-HTML contents (e.g. PDF documents).
 - (web::WebViewDocumentType)webViewDocumentType {
   // This happens during tests.
   if (!_wkWebView) {
     return web::WEB_VIEW_DOCUMENT_TYPE_GENERIC;
   }
 
-  std::string MIMEType = self.webState->GetContentsMimeType();
-  return [self documentTypeFromMIMEType:base::SysUTF8ToNSString(MIMEType)];
+  std::string mimeType = self.webState->GetContentsMimeType();
+  if (mimeType.empty()) {
+    return web::WEB_VIEW_DOCUMENT_TYPE_UNKNOWN;
+  }
+
+  if (mimeType == "text/html" || mimeType == "application/xhtml+xml" ||
+      mimeType == "application/xml") {
+    return web::WEB_VIEW_DOCUMENT_TYPE_HTML;
+  }
+
+  return web::WEB_VIEW_DOCUMENT_TYPE_GENERIC;
 }
 
 - (void)loadRequest:(NSMutableURLRequest*)request {
   [_wkWebView loadRequest:request];
 }
 
 - (void)loadWebHTMLString:(NSString*)html forURL:(const GURL&)URL {
   [_wkWebView loadHTMLString:html baseURL:net::NSURLWithGURL(URL)];
 }
 
@@ skipping 1364 matching lines @@
         runJavaScriptTextInputPanelWithPrompt:prompt
                                   defaultText:defaultText
                                    requestURL:requestURL
                             completionHandler:completionHandler];
   } else if (completionHandler) {
     completionHandler(nil);
   }
 }
 
 @end