Fix background for leading/trailing ToolbarButtons

This accounts for additional internal padding which is present for
leading/trailing buttons when maximized / in fullscreen.

Bug: None
Change-Id: If6841101172316174d2bce5b6091d2f31e9f197b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1903652
Commit-Queue: Peter Boström <pbos@chromium.org>
Commit-Queue: Caroline Rising <corising@chromium.org>
Auto-Submit: Peter Boström <pbos@chromium.org>
Reviewed-by: Caroline Rising <corising@chromium.org>
Cr-Commit-Position: refs/heads/master@{#713493}

chrome/browser/ui/views/toolbar/toolbar_button.cc

@@ -144,8 +144,9 @@ void ToolbarButton::UpdateColorsAndInsets() {
       highlight_color_animation_.GetBackgroundColor();
   if (background_color) {
     // ToolbarButtons are always the height the location bar.
-    const gfx::Insets bg_insets(
-        (height() - GetLayoutConstant(LOCATION_BAR_HEIGHT)) / 2);
+    const gfx::Insets bg_insets =
+        gfx::Insets((height() - GetLayoutConstant(LOCATION_BAR_HEIGHT)) / 2) +
+        *GetProperty(views::kInternalPaddingKey);
     SetBackground(views::CreateBackgroundFromPainter(
         views::Painter::CreateSolidRoundRectPainter(
             *background_color, highlight_radius, bg_insets)));