Fixes document type detection on iOS 9.

ios/web/web_state/ui/crw_web_controller.mm

Index: ios/web/web_state/ui/crw_web_controller.mm
diff --git a/ios/web/web_state/ui/crw_web_controller.mm b/ios/web/web_state/ui/crw_web_controller.mm
index d95db1dabe5641c956b231f5a927c4a8576410c1..cf924ce323a90bc745466713bd499fffc8d33b62 100644
--- a/ios/web/web_state/ui/crw_web_controller.mm
+++ b/ios/web/web_state/ui/crw_web_controller.mm
@@ -820,6 +820,16 @@ const NSTimeInterval kSnapshotOverlayTransition = 0.5;
   return [self webViewDocumentType] == web::WEB_VIEW_DOCUMENT_TYPE_HTML;
 }
 
+- (web::WebViewDocumentType)documentTypeFromMIMEType:(NSString*)MIMEType {

[Eugene But (OOO till 7-30), 2015/11/19 16:29:01]

NIT: Please try keeping the same order for interface and implementation methods
(I know we are inconsistent with this). 

F.e. if in the header |documentTypeFromMIMEType:| is placed after |foo|, then in
the implementation |documentTypeFromMIMEType:| should also be placed after
|foo|.

[stkhapugin, 2015/11/20 10:50:43]

Done.

+  if ([MIMEType isEqualToString:@"text/html"] ||
+      [MIMEType isEqualToString:@"application/xhtml+xml"] ||
+      [MIMEType isEqualToString:@"application/xml"]) {
+    return web::WEB_VIEW_DOCUMENT_TYPE_HTML;
+  }
+
+  return web::WEB_VIEW_DOCUMENT_TYPE_GENERIC;
+}
+
 // Stop doing stuff, especially network stuff. Close the request tracker.
 - (void)terminateNetworkActivity {
   DCHECK(!_isHalted);