Introduce web and email mode (DO NOT MERGE)

This change introduces new keyboard mode "webEmail" to honor
InputType.TYPE_TEXT_VARIATION_WEB_EMAIL_ADDRESS. In this mode, both
'@' key and TAB key appear on the keyboard.

The keyboard layouts will be modified with other change.

Bug: 4490948
Change-Id: I66f9bda4907da448db097e9c900199dfa700b16a
diff --git a/java/res/values/attrs.xml b/java/res/values/attrs.xml
index f0da274..fb4d97b 100644
--- a/java/res/values/attrs.xml
+++ b/java/res/values/attrs.xml
@@ -167,6 +167,8 @@
             <enum name="im" value="3" />
             <enum name="web" value="4" />
             <enum name="phone" value="5" />
+            <enum name="number" value="6" />
+            <enum name="webEmail" value="7" />
         </attr>
         <attr name="passwordInput" format="boolean" />
         <attr name="hasSettingsKey" format="string" />