[Android] Add more context to sign-in promo description strings

This CL changes the descriptions of the strings used in personalized
sign-in promos to add more context for the translators.

Bug: b/111761802
Change-Id: If1064ce114f1c7f4998f4afcce4d65b49a0e8629
Reviewed-on: https://chromium-review.googlesource.com/1152976Reviewed-by: Bernhard Bauer <bauerb@chromium.org>
Commit-Queue: Boris Sazonov <bsazonov@chromium.org>
Cr-Commit-Position: refs/heads/master@{#578649}

chrome/android/java/strings/android_chrome_strings.grd

@@ -2624,10 +2624,10 @@ To obtain new licenses, connect to the internet and play your downloaded content
       <message name="IDS_SIGNIN_PROMO_DESCRIPTION_RECENT_TABS_NO_ACCOUNT" desc="Description string for 'Continue as' signin promo shown in Recent Tabs screen. This version of the string is shown when there are no accounts on the device.">
         To get your tabs from your other devices, sign in and turn on sync
       </message>
-      <message name="IDS_SIGNIN_PROMO_DESCRIPTION_SETTINGS" desc="Description string for 'Continue as' signin promo shown in Settings screen.">
+      <message name="IDS_SIGNIN_PROMO_DESCRIPTION_SETTINGS" desc="Description string for 'Continue as' signin promo shown in Settings screen. Turning on sync enables syncing browser settings, autofill data, bookmarks, passwords, history and other data used for browser personalization.">
         To sync and personalize across devices, turn on sync
       </message>
-      <message name="IDS_SIGNIN_PROMO_DESCRIPTION_SETTINGS_NO_ACCOUNT" desc="Description string for 'Continue as' signin promo shown in Settings screen. This version of the string is shown when there are no accounts on the device.">
+      <message name="IDS_SIGNIN_PROMO_DESCRIPTION_SETTINGS_NO_ACCOUNT" desc="Description string for 'Continue as' signin promo shown in Settings screen. This version of the string is shown when there are no accounts on the device. Turning on sync enables syncing browser settings, autofill data, bookmarks, passwords, history and other data used for browser personalization.">
         To sync and personalize across devices, sign in and turn on sync
       </message>
       <message name="IDS_SIGNIN_PROMO_CHOOSE_ANOTHER_ACCOUNT" desc="Button that the user can press if they want to select a different account before signing in. This button is shown below 'Continue as Joe Doe' button that signs user in with default account.">