[AF] Fix label vertical alignment on Autofill dropdown

This changes the cross axis alignment for the suggestion view's
BoxLayout to CROSS_AXIS_ALIGNMENT_STRETCH, so that labels will
vertically center themselves on the view.

Screenshots (Googlers only): https://drive.google.com/open?id=1Cfn9vBcJahBGj9oSl_5xRwBt9LDINa60

Bug: 850971
Change-Id: I877988889a6d0a3a07dbca34cb194bd3eef0668a
Reviewed-on: https://chromium-review.googlesource.com/1142371Reviewed-by: Evan Stade <estade@chromium.org>
Commit-Queue: Fabio Tirelo <ftirelo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#576517}

chrome/browser/ui/views/autofill/autofill_popup_view_native_views.cc

@@ -268,7 +268,7 @@ void AutofillPopupItemView::CreateContent() {
       views::BoxLayout::kHorizontal, gfx::Insets(0, GetHorizontalMargin())));
 
   layout->set_cross_axis_alignment(
-      views::BoxLayout::CrossAxisAlignment::CROSS_AXIS_ALIGNMENT_CENTER);
+      views::BoxLayout::CrossAxisAlignment::CROSS_AXIS_ALIGNMENT_STRETCH);
   layout->set_minimum_cross_axis_size(
       views::MenuConfig::instance().touchable_menu_height + extra_height_);