Collapsible offline content list on dino page

Allows the offline content list on the dino page to be collapsed by the
user, mirroring the UX used on the NTP for collapsing the list of
suggested articles.

These two collapsible lists also share the same PrefsService setting so
that the expanded/collapsed state of one is reflected on the other.

This also fixes a small issue with the background color appearing
between a suggestion image and its border.

Bug: 852872
Change-Id: I47ed7abaa777fe233ec79153a033482812ae478a
Reviewed-on: https://chromium-review.googlesource.com/c/1318630
Reviewed-by: Min Qin <[email protected]>
Reviewed-by: Cathy Li <[email protected]>
Reviewed-by: Greg Kerr <[email protected]>
Reviewed-by: Matt Menke <[email protected]>
Reviewed-by: Cait Phillips <[email protected]>
Reviewed-by: Dan H <[email protected]>
Reviewed-by: Edward Jung <[email protected]>
Commit-Queue: Carlos Knippschild <[email protected]>
Cr-Commit-Position: refs/heads/master@{#609837}
diff --git a/components/components_strings.grd b/components/components_strings.grd
index d539c1a..045961b 100644
--- a/components/components_strings.grd
+++ b/components/components_strings.grd
@@ -242,6 +242,14 @@
       <message name="IDS_SAVE" desc="Used on a button to save information you are editing.">
         Save
       </message>
+      <if expr="is_android">
+        <message name="IDS_SHOW" desc="Generic label to show content for a feature. [CHAR-LIMIT=20]" formatter_data="android_java">
+          Show
+        </message>
+        <message name="IDS_HIDE" desc="Generic label to hide content for a feature. [CHAR-LIMIT=20]" formatter_data="android_java">
+          Hide
+        </message>
+      </if>
       <if expr="not use_titlecase">
         <message name="IDS_NO_THANKS" desc="Used to dismiss various prompts.">
           No thanks