Set transparent arrow for IntentPickerBubbleView

This one-liner is to make this UI looks like the spec, also the other
bubbles on the omnibox doesn't have a visible arrow.

Bug: None.
Test: Build, also on an ARC device enabled poked around with pinterest.
Change-Id: Iad9913d68d86b9a276f793b5a34962644c836344
Reviewed-on: https://chromium-review.googlesource.com/978671Reviewed-by: Scott Violet <sky@chromium.org>
Commit-Queue: David Jacobo <djacobo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#545601}

chrome/browser/ui/views/intent_picker_bubble_view.cc

@@ -148,6 +148,8 @@ views::Widget* IntentPickerBubbleView::ShowBubble(
   }
   views::Widget* widget =
       views::BubbleDialogDelegateView::CreateBubble(intent_picker_bubble_);
+  intent_picker_bubble_->SetArrowPaintType(
+      views::BubbleBorder::PAINT_TRANSPARENT);
   intent_picker_bubble_->GetDialogClientView()->Layout();
   intent_picker_bubble_->SetFocusBehavior(View::FocusBehavior::ALWAYS);
   intent_picker_bubble_->GetIntentPickerLabelButtonAt(0)->MarkAsSelected(