Fixes document type detection on iOS 9.

ios/web/web_state/ui/crw_wk_web_view_web_controller.mm

Index: ios/web/web_state/ui/crw_wk_web_view_web_controller.mm
diff --git a/ios/web/web_state/ui/crw_wk_web_view_web_controller.mm b/ios/web/web_state/ui/crw_wk_web_view_web_controller.mm
index 368587eab562249bab292466ff34a608391942d3..fec4c7154a4bc57b9d0340bf27b46136ebb69599 100644
--- a/ios/web/web_state/ui/crw_wk_web_view_web_controller.mm
+++ b/ios/web/web_state/ui/crw_wk_web_view_web_controller.mm
@@ -42,8 +42,8 @@
 #import "ios/web/web_state/web_view_internal_creation_util.h"
 #import "ios/web/web_state/wk_web_view_security_util.h"
 #import "ios/web/webui/crw_web_ui_manager.h"
-#include "net/cert/x509_certificate.h"
 #import "net/base/mac/url_conversions.h"
+#include "net/cert/x509_certificate.h"
 #include "net/ssl/ssl_info.h"
 #include "url/url_constants.h"
 
@@ -435,13 +435,7 @@ WKWebViewErrorSource WKWebViewErrorSourceFromError(NSError* error) {
     return web::WEB_VIEW_DOCUMENT_TYPE_UNKNOWN;
   }
 
-  if ([self.documentMIMEType isEqualToString:@"text/html"] ||
-      [self.documentMIMEType isEqualToString:@"application/xhtml+xml"] ||
-      [self.documentMIMEType isEqualToString:@"application/xml"]) {
-    return web::WEB_VIEW_DOCUMENT_TYPE_HTML;
-  }
-
-  return web::WEB_VIEW_DOCUMENT_TYPE_GENERIC;
+  return [self documentTypeFromMIMEType:self.documentMIMEType];
 }
 
 - (void)loadRequest:(NSMutableURLRequest*)request {