[omnibox] Adjust header to collaspe chevron spacing to 8px

This spacing was provided by the designer and matches the realbox.

Bug: 1128160
Change-Id: Ia5b4af4cbab04cf1b3a07eb2fa49e40a579d82be
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2422478
Auto-Submit: Tommy Li <tommycli@chromium.org>
Reviewed-by: Moe Ahmadi <mahmadi@chromium.org>
Commit-Queue: Moe Ahmadi <mahmadi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#809004}

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

@@ -44,9 +44,8 @@ class OmniboxRowView::HeaderView : public views::View,
     views::BoxLayout* layout =
         SetLayoutManager(std::make_unique<views::BoxLayout>(
             views::BoxLayout::Orientation::kHorizontal));
-    // The icons in the header view match their sizing to the location bar.
-    layout->set_between_child_spacing(
-        GetLayoutConstant(LOCATION_BAR_CHILD_INTERIOR_PADDING));
+    // This is the designer-provided spacing that matches the NTP Realbox.
+    layout->set_between_child_spacing(8);
 
     header_label_ = AddChildView(std::make_unique<views::Label>());
     header_label_->SetHorizontalAlignment(gfx::HorizontalAlignment::ALIGN_LEFT);