Volume A11y: Prevent auto-dismiss when feedback enabled.

 - Prevent the volume dialog from timing out when feedback is enabled.
 - Use the a11y events as an additional user activity signal.
 - Add content descriptions for the dialog icon buttons.

Bug: 20172022
Change-Id: Id5cd29d9cee27fded2fc8a029913cfcc2b68c152
diff --git a/packages/SystemUI/res/values/strings.xml b/packages/SystemUI/res/values/strings.xml
index 80fecac..b836af6 100644
--- a/packages/SystemUI/res/values/strings.xml
+++ b/packages/SystemUI/res/values/strings.xml
@@ -951,6 +951,12 @@
     <!-- Button label for ending zen mode in the volume dialog -->
     <string name="volume_zen_end_now">End now</string>
 
+    <!-- Content description for accessibility (not shown on the screen): volume dialog expand button. [CHAR LIMIT=NONE] -->
+    <string name="accessibility_volume_expand">Expand</string>
+
+    <!-- Content description for accessibility (not shown on the screen): volume dialog collapse button. [CHAR LIMIT=NONE] -->
+    <string name="accessibility_volume_collapse">Collapse</string>
+
     <!-- Screen pinning dialog title. -->
     <string name="screen_pinning_title">Screen is pinned</string>
     <!-- Screen pinning dialog description. -->