Fix intent picker apps background colour.

Currently, the background color for the scroll_view in the intent picker
bubble is set to be always white. However, when the theme is different,
the bubble background could be different. This CL changes the color to
theme background color.

BUG=987542

Change-Id: I3f081cd62f15e804f3e639b96d76f3797080e646
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1720331
Reviewed-by: Scott Violet <sky@chromium.org>
Commit-Queue: Maggie Cai <mxcai@chromium.org>
Cr-Commit-Position: refs/heads/master@{#682051}

diff --git a/chrome/browser/ui/views/intent_picker_bubble_view.cc b/chrome/browser/ui/views/intent_picker_bubble_view.cc
index f79efbd..172be55 100644
--- a/chrome/browser/ui/views/intent_picker_bubble_view.cc
+++ b/chrome/browser/ui/views/intent_picker_bubble_view.cc

@@ -358,7 +358,8 @@
     app_info_.erase(app_info_.begin() + to_erase);
 
   auto scroll_view = std::make_unique<views::ScrollView>();
-  scroll_view->SetBackgroundColor(SK_ColorWHITE);
+  scroll_view->SetBackgroundThemeColorId(
+      ui::NativeTheme::kColorId_BubbleBackground);
   scroll_view->SetContents(std::move(scrollable_view));
   // This part gives the scroll a fixed width and height. The height depends on
   // how many app candidates we got and how many we actually want to show.