[android] Scan new credit card from autofill popup.

This patch adds a "Scan new card" menu item to the autofill popup on
Android. The feature is behind the command line flag:

  --enable-credit-card-scan

BUG=428085

Review URL: https://codereview.chromium.org/700623004

Cr-Commit-Position: refs/heads/master@{#305869}
diff --git a/components/autofill_strings.grdp b/components/autofill_strings.grdp
index 5a3fd5ed..bb95163 100644
--- a/components/autofill_strings.grdp
+++ b/components/autofill_strings.grdp
@@ -124,4 +124,8 @@
     </message>
   </if>
 
+  <message name="IDS_AUTOFILL_SCAN_CREDIT_CARD" desc="An item in the autofill popup that triggers a new credit card to be scanned using the camera on the device.">
+    Scan new card
+  </message>
+
 </grit-part>