Separate string for Compose action bar title

Add new string and set limit to 10 chars (from
my testing 10 is a the safe number depending
on what characters are used).

b/16873798

Change-Id: I9e98230267d6621abe2201077df8aee8d1f69928
diff --git a/res/values/strings.xml b/res/values/strings.xml
index 67af422..2fd809c 100644
--- a/res/values/strings.xml
+++ b/res/values/strings.xml
@@ -56,6 +56,8 @@
     <string name="discard">Discard</string>
     <!-- The possible ways to reply to a message [CHAR LIMIT=15] -->
     <string name="compose">Compose</string>
+    <!-- The action bar title for  the default compose mode [CHAR LIMIT=10] -->
+    <string name="compose_title">Compose</string>
     <!-- The possible ways to reply to a message [CHAR LIMIT=15] -->
     <string-array name="compose_modes">
         <!-- Reply -->