Return new background drawable rather than caching in CardConfiguration

TBR=huayinz@chromium.org
BUG=891089

Change-Id: I4d4c6fbdb2d845b0639f0eab05f4b043a2a9a15e
Reviewed-on: https://chromium-review.googlesource.com/1256108
Commit-Queue: Theresa <twellington@chromium.org>
Reviewed-by: Theresa <twellington@chromium.org>
Cr-Commit-Position: refs/heads/master@{#595697}

chrome/android/feed/core/java/src/org/chromium/chrome/browser/feed/FeedNewTabPage.java

@@ -120,7 +120,6 @@ public class FeedNewTabPage extends NewTabPage {
         private final Resources mResources;
         private final UiConfig mUiConfig;
         private final int mCornerRadius;
-        private final Drawable mCardBackground;
         private final int mCardMargin;
         private final int mCardWideMargin;
 
@@ -129,8 +128,6 @@ public class FeedNewTabPage extends NewTabPage {
             mUiConfig = uiConfig;
             mCornerRadius = mResources.getDimensionPixelSize(
                     R.dimen.content_suggestions_card_modern_corner_radius);
-            mCardBackground = ApiCompatibilityUtils.getDrawable(
-                    mResources, R.drawable.content_card_modern_background);
             mCardMargin = mResources.getDimensionPixelSize(
                     R.dimen.content_suggestions_card_modern_margin);
             mCardWideMargin =
@@ -144,7 +141,8 @@ public class FeedNewTabPage extends NewTabPage {
 
         @Override
         public Drawable getCardBackground() {
-            return mCardBackground;
+            return ApiCompatibilityUtils.getDrawable(
+                    mResources, R.drawable.content_card_modern_background);
         }
 
         @Override