Add the about_page key to shared_module manifest

chrome/app/generated_resources.grd

Index: chrome/app/generated_resources.grd
diff --git a/chrome/app/generated_resources.grd b/chrome/app/generated_resources.grd
index 2168a3880cfc58a635f67beecfd93be9fc68789f..5c7c1da1c867340f26455d8329d3cb910dc94c07 100644
--- a/chrome/app/generated_resources.grd
+++ b/chrome/app/generated_resources.grd
@@ -4551,6 +4551,9 @@ Make sure you do not expose any sensitive information.
       <message name="IDS_EXTENSION_LOAD_OPTIONS_PAGE_FAILED" desc="">
         Could not load options page '<ph name="OPTIONS_PAGE">$1<ex>page.html</ex></ph>'.
       </message>
+      <message name="IDS_EXTENSION_LOAD_ABOUT_PAGE_FAILED" desc="">
+        Could not load about page '<ph name="ABOUT_PAGE">$1<ex>page.html</ex></ph>'.
+      </message>
       <if expr="is_win">
         <message name="IDS_EXTENSION_UNPACK_FAILED" desc="On windows, it is possible to mount a disk without the root of that disk having a drive letter.  The sandbox does not support this. See crbug/49530 .">
           Can not unpack extension.  To safely unpack an extension, there must be a path to your profile directory that starts with a drive letter and does not contain a junction, mount point, or symlink.  No such path exists for your profile.