[MDM] Fix for incognito mode menu item

The incognito restriction was correctly gating incognito tab creation when
attempted from the 'new tab' screen, but I had missed the incognito icon
at the top of the menu.

The fix was to modify the IncognitoRestriction class to manage a new type
of control (the menu icon) and to push the gating logic down into the
Controller class (where it really belongs anyway).

Change-Id: I5395f060502907fcc7d03826568af1802450ad1b
diff --git a/src/com/android/browser/NavScreen.java b/src/com/android/browser/NavScreen.java
index 76d0703..d8bfd56 100644
--- a/src/com/android/browser/NavScreen.java
+++ b/src/com/android/browser/NavScreen.java
@@ -33,7 +33,6 @@
 import android.widget.PopupMenu;
 import android.widget.PopupMenu.OnMenuItemClickListener;
 import android.widget.RelativeLayout;
-import android.widget.Toast;
 
 import com.android.browser.NavTabScroller.OnRemoveListener;
 import com.android.browser.mdm.IncognitoRestriction;
@@ -117,7 +116,7 @@
                 R.string.accessibility_transition_navscreen));
         mToolbarLayout = findViewById(R.id.nav_toolbar_animate);
         mNewIncognitoTab = (ImageButton) findViewById(R.id.newincognitotab);
-        IncognitoRestriction.getInstance().registerButton(mNewIncognitoTab);
+        IncognitoRestriction.getInstance().registerControl(mNewIncognitoTab);
         mNewTab = (ImageButton) findViewById(R.id.newtab);
         mMore = (ImageButton) findViewById(R.id.more);
         mNewIncognitoTab.setOnClickListener(this);
@@ -149,11 +148,7 @@
         if (mNewTab == v) {
             openNewTab();
         } else if (mNewIncognitoTab == v) {
-            if (IncognitoRestriction.getInstance().isEnabled()) {
-                Toast.makeText(getContext(), R.string.mdm_managed_alert, Toast.LENGTH_SHORT).show();
-            } else {
-                openNewIncognitoTab();
-            }
+            openNewIncognitoTab();
         } else if (mMore == v) {
             showPopupMenu();
         }