Remove "paste as plain text" from selection menu

"paste as plain text" introduced an empty option in selection menu due
to the runtime string resource setting. Since we need to update
|canEditRichly| flag for the option in selection menu, there is no
simple way to do so right now, so simply remove this option.
Need to add it back later.

BUG=718330

Review-Url: https://codereview.chromium.org/2858333002
Cr-Commit-Position: refs/heads/master@{#469483}

content/public/android/java/src/org/chromium/content/browser/SelectionPopupController.java

@@ -484,6 +484,10 @@ public class SelectionPopupController extends ActionModeCallbackHelper {
 
         updateAssistMenuItem(descriptor);
 
+        // TODO(ctzsm): Remove "paste as plain text" for now, need to add it back when
+        // crrev.com/2785853002 landed.
+        descriptor.removeItem(R.id.select_action_menu_paste_as_plain_text);
+
         if (!isSelectionEditable() || !canPaste()) {
             descriptor.removeItem(R.id.select_action_menu_paste);
         }