Change tab switcher button content description

TalkBack does not explain how to open a new tab in Chrome when focusing
the tabs button in the toolbar. Updated the content description for
this button to communicate how to open new tabs

Bug: 851175
Change-Id: I6dc16d09fe0a2a2902401e9e3060eaef91913e35
Reviewed-on: https://chromium-review.googlesource.com/c/1330759
Commit-Queue: Theresa <twellington@chromium.org>
Reviewed-by: Theresa <twellington@chromium.org>
Cr-Commit-Position: refs/heads/master@{#612417}

chrome/android/java/strings/android_chrome_strings.grd

@@ -3285,7 +3285,7 @@ To change this setting, <ph name="BEGIN_LINK">&lt;resetlink&gt;</ph>reset sync<p
         New private tab
       </message>
       <message name="IDS_ACCESSIBILITY_TOOLBAR_BTN_TABSWITCHER_TOGGLE" desc="Content description for the button that enters or leaves the tab switcher. [ICU Syntax]">
-        {OPEN_TABS, plural, =1 {%1$d open tab} other {%1$d open tabs}}
+        {OPEN_TABS, plural, =1 {%1$d open tab, tap to switch tabs} other {%1$d open tabs, tap to switch tabs}}
       </message>
       <message name="IDS_ACCESSIBILITY_TOOLBAR_BTN_TABSWITCHER_TOGGLE_DEFAULT" desc="Placeholder content description for the button that enters or leaves the tab switcher.">
         open tabs