Hook up Ctrl + '/' to SysUI for a Keyboard Shortcuts screen

This CL adds the necessary hooks between PhoneWindowManager
and SysUI to show a keyboard shortcuts screen given a specific
shortcut combination. SysUI for now just shows a Toast.

Change-Id: Icf43a81776b04a2e96a540f45b7cd3464342d679
diff --git a/packages/SystemUI/src/com/android/systemui/statusbar/CommandQueue.java b/packages/SystemUI/src/com/android/systemui/statusbar/CommandQueue.java
index a1b07b5..d0cd6cb 100644
--- a/packages/SystemUI/src/com/android/systemui/statusbar/CommandQueue.java
+++ b/packages/SystemUI/src/com/android/systemui/statusbar/CommandQueue.java
@@ -64,6 +64,7 @@
     private static final int MSG_APP_TRANSITION_STARTING    = 21 << MSG_SHIFT;
     private static final int MSG_ASSIST_DISCLOSURE          = 22 << MSG_SHIFT;
     private static final int MSG_START_ASSIST               = 23 << MSG_SHIFT;
+    private static final int MSG_SHOW_KEYBOARD_SHORTCUTS    = 24 << MSG_SHIFT;
 
     public static final int FLAG_EXCLUDE_NONE = 0;
     public static final int FLAG_EXCLUDE_SEARCH_PANEL = 1 << 0;
@@ -98,6 +99,7 @@
         public void hideRecentApps(boolean triggeredFromAltTab, boolean triggeredFromHomeKey);
         public void toggleRecentApps();
         public void preloadRecentApps();
+        public void showKeyboardShortcutsMenu();
         public void cancelPreloadRecentApps();
         public void setWindowState(int window, int state);
         public void buzzBeepBlinked();
@@ -224,6 +226,14 @@
         }
     }
 
+    @Override
+    public void showKeyboardShortcutsMenu() {
+        synchronized (mList) {
+            mHandler.removeMessages(MSG_SHOW_KEYBOARD_SHORTCUTS);
+            mHandler.obtainMessage(MSG_SHOW_KEYBOARD_SHORTCUTS).sendToTarget();
+        }
+    }
+
     public void setWindowState(int window, int state) {
         synchronized (mList) {
             // don't coalesce these
@@ -360,6 +370,9 @@
                 case MSG_CANCEL_PRELOAD_RECENT_APPS:
                     mCallbacks.cancelPreloadRecentApps();
                     break;
+                case MSG_SHOW_KEYBOARD_SHORTCUTS:
+                    mCallbacks.showKeyboardShortcutsMenu();
+                    break;
                 case MSG_SET_WINDOW_STATE:
                     mCallbacks.setWindowState(msg.arg1, msg.arg2);
                     break;