Add reader mode option in popup menu

Reader mode use the DOM distiller to load the distilled version of a webpage
Reader mode is disabled by default and will be available only with the use
of the command line flag "reader-mode"

Change-Id: Ide36057cae4e71b94e8118cc767f600cd610b82e
diff --git a/res/menu/browser.xml b/res/menu/browser.xml
index af57357..60e9e78 100644
--- a/res/menu/browser.xml
+++ b/res/menu/browser.xml
@@ -80,6 +80,12 @@
                 android:id="@+id/ua_desktop_menu_id"
                 android:checkable="true"
                 android:title="@string/ua_switcher_desktop" />
+
+            <item
+                android:id="@+id/reader_mode_menu_id"
+                android:checkable="true"
+                android:title="@string/enable_reader_mode" />
+
             <item
                 android:id="@+id/save_snapshot_menu_id"
                 android:title="@string/menu_save_snapshot" />