Fix iOS omnibox append button highlighted icon for RTL

The omnibox append button's normal (un-highlighted) image is correctly
reversed for RTL languages, but the imaged displayed when the button is
tapped is not.

BUG=678085

Review-Url: https://codereview.chromium.org/2606353004
Cr-Commit-Position: refs/heads/master@{#441418}

ios/chrome/browser/ui/omnibox/omnibox_popup_material_row.mm

@@ -162,7 +162,8 @@ const CGFloat kAppendButtonTrailingMargin = 4;
   int appendSelectedResourceID =
       _incognito ? IDR_IOS_OMNIBOX_KEYBOARD_VIEW_APPEND_INCOGNITO_HIGHLIGHTED
                  : IDR_IOS_OMNIBOX_KEYBOARD_VIEW_APPEND_HIGHLIGHTED;
-  UIImage* appendImageSelected = NativeImage(appendSelectedResourceID);
+  UIImage* appendImageSelected =
+      NativeReversableImage(appendSelectedResourceID, YES);
   [_appendButton setImage:appendImageSelected
                  forState:UIControlStateHighlighted];
 }