ChromeLabs: Darkmode for relaunch footer

Bug: 1157313
Change-Id: I7a178d3b8dcb87e2e77b4ef74fffb77480200989
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2585713Reviewed-by: Robert Liao <robliao@chromium.org>
Reviewed-by: Allen Bauer <kylixrd@chromium.org>
Commit-Queue: Elaine Chien <elainechien@chromium.org>
Cr-Commit-Position: refs/heads/master@{#836187}

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

@@ -89,7 +89,8 @@ class ChromeLabsFooter : public views::View {
                      .SetCallback(base::BindRepeating(&chrome::AttemptRestart))
                      .SetText(base::ASCIIToUTF16("Relaunch"))
                      .Build());
-    SetBackground(views::CreateSolidBackground(gfx::kGoogleGrey200));
+    SetBackground(views::CreateThemedSolidBackground(
+        this, ui::NativeTheme::kColorId_BubbleFooterBackground));
     SetBorder(views::CreateEmptyBorder(
         views::LayoutProvider::Get()->GetInsetsMetric(views::INSETS_DIALOG)));
     SetProperty(