Add callout for the tab switcher button

chrome/android/java/strings/android_chrome_strings.grd

Index: chrome/android/java/strings/android_chrome_strings.grd
diff --git a/chrome/android/java/strings/android_chrome_strings.grd b/chrome/android/java/strings/android_chrome_strings.grd
index 6574c534d5100b9b48a66fed5330452b4a0930db..d052790231b00c53f0609bc2ff280c70ae3131b6 100644
--- a/chrome/android/java/strings/android_chrome_strings.grd
+++ b/chrome/android/java/strings/android_chrome_strings.grd
@@ -2358,6 +2358,14 @@ You can control the Physical Web in Chrome Settings.
       <message name="IDS_PAYMENTS_ERROR_MESSAGE" desc="The text that informs the user that there is error in verifying and charging the payment.">
         Error processing payment
       </message>
+
+      <!-- Migration strings -->
+      <message name="IDS_TAB_SWITCHER_CALLOUT_HEADER" desc="Header for the Tab Switcher callout.">
+        Quickly switch tabs
+      </message>
+      <message name="IDS_TAB_SWITCHER_CALLOUT_BODY" desc="Indicates that clicking the tab switcher button gives you quick access to your tabs.">
+        Tap this button for quick access to your tabs.
+      </message>
     </messages>
   </release>
 </grit>