[Overlay] Update bar background color

Updates the Bar background color in both the old and new layout
to match the color used in the top_round assets.

BUG=1005558

Change-Id: I8ccd5176039f386ff9df918c1894732185c37916
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1817152Reviewed-by: Matthew Jones <mdjones@chromium.org>
Commit-Queue: Donn Denman <donnd@chromium.org>
Cr-Commit-Position: refs/heads/master@{#698956}

chrome/android/java/res/values/colors.xml

@@ -104,7 +104,7 @@
     <color name="incognito_emphasis">@android:color/white</color>
 
     <!-- Overlay Panel colors -->
-    <color name="overlay_panel_bar_background_color">@color/default_bg_color_elev_2</color>
+    <color name="overlay_panel_bar_background_color">@color/default_bg_color_elev_4</color>
     <color name="overlay_panel_separator_line_color">@color/modern_secondary_color</color>
 
     <!-- Contextual Search colors -->