Update assets for new tab.

Also remove the old one and an obsolete file which references it.

Fixes http://b/issue?id=2099961

Change-Id: I92e08fcc07826d5bde7ddb87c71932de2e01b778
diff --git a/res/menu/browser.xml b/res/menu/browser.xml
index c2814c8..4a73261 100644
--- a/res/menu/browser.xml
+++ b/res/menu/browser.xml
@@ -20,7 +20,7 @@
             android:alphabeticShortcut="r" />
         <item android:id="@+id/new_tab_menu_id"
             android:title="@string/new_tab"
-            android:icon="@drawable/ic_add_tab"
+            android:icon="@drawable/ic_menu_new_window"
             android:alphabeticShortcut="n" />
         <item android:id="@+id/active_tabs_menu_id"
             android:title="@string/active_tabs"