Implemented new channel switcher UI.

chrome/app/chromium_strings.grd

Index: chrome/app/chromium_strings.grd
diff --git a/chrome/app/chromium_strings.grd b/chrome/app/chromium_strings.grd
index 2c3a10464c62a42ae25e7de63e54910329a5bcb7..d409ab2c2e464c92c47924c15aa64d472c15a8a9 100644
--- a/chrome/app/chromium_strings.grd
+++ b/chrome/app/chromium_strings.grd
@@ -724,6 +724,11 @@ For Chromium, processes used to display diagnostics information (such as this "a
           Nearly up-to-date! Restart your device to finish updating.
         </message>
       </if>
+      <if expr="pp_ifdef('chromeos')">
+        <message name="IDS_UPGRADE_SUCCESSFUL_CHANNEL_SWITCH" desc="Status label: Channel was successfully switched on Chromium OS">
+          Channel changed. Restart your device to apply changes.
+        </message>
+      </if>
       <if expr="not pp_ifdef('chromeos')">
         <message name="IDS_UPGRADE_UP_TO_DATE" desc="Status label: Already up to date (Chromium)">
           Chromium is up to date.
@@ -744,6 +749,11 @@ For Chromium, processes used to display diagnostics information (such as this "a
           Updating your device...
         </message>
       </if>
+      <if expr="pp_ifdef('chromeos')">
+        <message name="IDS_UPGRADE_UPDATING_CHANNEL_SWITCH" desc="Status label: Updating Chromium OS to a specified channel">
+          Updating your device to <ph name="CHANNEL_NAME">$1<ex>stable</ex></ph> channel...
+        </message>
+      </if>
 
       <!-- iOS Upgrade available info bar-->
       <if expr="pp_ifdef('ios')">