Add a notice about other forms of browsing history to the History WebUI.

components/history_strings.grdp

Index: components/history_strings.grdp
diff --git a/components/history_strings.grdp b/components/history_strings.grdp
index 74633486239d59b0782c75206d5d12d3da703cbf..39bee6af98aba2cc3573e9fd3732f438f2ec7d79 100644
--- a/components/history_strings.grdp
+++ b/components/history_strings.grdp
@@ -55,6 +55,9 @@ Psst! Incognito mode <ph name="SHORTCUT_KEY">$1<ex>(Ctrl+Shift+N)</ex></ph> may
   <message name="IDS_HISTORY_HAS_SYNCED_RESULTS" desc="The notification at the top of the history page indicating that it is showing visits synced from other devices.">
     Showing history from your signed-in devices. <ph name="BEGIN_LINK">&lt;a href="https://support.google.com/chrome/?p=sync_history&amp;hl=[GRITLANGCODE]"&gt;</ph>Learn more<ph name="END_LINK">&lt;/a&gt;<ex>&lt;/a&gt;</ex></ph>
   </message>
+  <message name="IDS_HISTORY_OTHER_FORMS_OF_HISTORY" desc="The notification at the top of the history page indicating that deleting Chrome browsing history will not delete other forms of history stored at Google My Activity.">
+    Other forms of browsing history are still available at <ph name="BEGIN_LINK">&lt;a target="_blank" href="$1"&gt;</ph>Google My Activity<ph name="END_LINK">&lt;/a&gt;</ph>.
+  </message>
   <message name="IDS_HISTORY_IN_CONTENT_PACK" desc="Text that shows that an entry is in a content pack.">
     In content pack
   </message>