Use the screenshot theme on wmshell screenshot tests

* This ensures screenshots in the tests are taken with light & dark
  theme
* Additionally, set a background color on the activity in our
  user education test -- otherwise the colors in the education views
  match the background of the activity and we miss the outline of
  the arrow & rounded corners on the view

Flag: EXEMPT test change
Test: atest --request-upload-result WMShellRobolectricScreenshotTests:com.android.wm.shell.bubbles.BubbleEducationViewScreenshotTest
      & inspect the screenshots in the uploaded result (ran on acloud device)
Bug: 375030558
Change-Id: Ide7eb87b8d05fb3b8930ec21644ca5429a41c34a
diff --git a/libs/WindowManager/Shell/multivalentScreenshotTests/Android.bp b/libs/WindowManager/Shell/multivalentScreenshotTests/Android.bp
index b6db6d9..61c09f2 100644
--- a/libs/WindowManager/Shell/multivalentScreenshotTests/Android.bp
+++ b/libs/WindowManager/Shell/multivalentScreenshotTests/Android.bp
@@ -29,6 +29,8 @@
     static_libs: [
         "WindowManager-Shell",
         "platform-screenshot-diff-core",
+        "ScreenshotComposeUtilsLib", // ComposableScreenshotTestRule & Theme.PlatformUi.Screenshot
+        "SystemUI-res", // Theme.SystemUI (dragged in by ScreenshotComposeUtilsLib)
     ],
     asset_dirs: ["goldens/robolectric"],
     manifest: "AndroidManifestRobolectric.xml",
@@ -63,6 +65,8 @@
     ],
     static_libs: [
         "WindowManager-Shell",
+        "ScreenshotComposeUtilsLib", // ComposableScreenshotTestRule & Theme.PlatformUi.Screenshot
+        "SystemUI-res", // Theme.SystemUI (dragged in by ScreenshotComposeUtilsLib)
         "junit",
         "androidx.test.runner",
         "androidx.test.rules",