[Feed] Suppress UnusedResources warning on hairline asset

Suppress unused resource lint warning so that compilation without the
Feed enable doesn't fail.

BUG=951074

Change-Id: Iac74b2bd29cc54c976d7112101a5ab814a10898e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1566286
Auto-Submit: Theresa <twellington@chromium.org>
Reviewed-by: Sky Malice <skym@chromium.org>
Commit-Queue: Theresa <twellington@chromium.org>
Cr-Commit-Position: refs/heads/master@{#650510}

chrome/android/java/res/drawable/hairline_border_card_background_with_inset.xml

@@ -3,8 +3,11 @@
      Use of this source code is governed by a BSD-style license that can be
      found in the LICENSE file. -->
 
+<!-- TODO(twellington): Remove tools:ignore after feed build flag is removed -->
 <shape
     xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:tools="http://schemas.android.com/tools"
+    tools:ignore="UnusedResources"
     android:shape="rectangle" >
     <solid android:color="@color/modern_primary_color" />
     <stroke android:width="1dp" android:color="@color/hairline_stroke_color"/>