[omnibox] Change popup bottom margin from 4dp => 8dp

UX folks suggested 8dp instead for aesthetic reasons.

Bug: 1078415
Change-Id: I56ab151c4147b10b8853ebf1b9ae22cf1f4af90b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2265180
Auto-Submit: Tommy Li <tommycli@chromium.org>
Reviewed-by: manuk hovanesian <manukh@chromium.org>
Commit-Queue: Tommy Li <tommycli@chromium.org>
Cr-Commit-Position: refs/heads/master@{#782109}

chrome/browser/ui/views/omnibox/omnibox_popup_contents_view.cc

@@ -495,9 +495,10 @@ gfx::Rect OmniboxPopupContentsView::GetTargetBounds() {
   // interior between each row of text.
   popup_height += RoundedOmniboxResultsFrame::GetNonResultSectionHeight();
 
-  // Add 4dp at the bottom for aesthetic reasons. https://crbug.com/1076646
+  // Add 8dp at the bottom for aesthetic reasons. https://crbug.com/1076646
   // It's expected that this space is dead unclickable/unhighlightable space.
-  popup_height += 4;
+  constexpr int kExtraBottomPadding = 8;
+  popup_height += kExtraBottomPadding;
 
   // The rounded popup is always offset the same amount from the omnibox.
   gfx::Rect content_rect = location_bar_view_->GetBoundsInScreen();