Adds a cancel button to ShortcutActivity dialog

 Bug: 3167402
 Adds a cancel button to the ShortcutActivity when it is being
 shown as a dialog (when large)

Change-Id: I6e47db8770cd18f69d534c361ff8fc90128e8dad
diff --git a/src/com/android/browser/BrowserBookmarksPage.java b/src/com/android/browser/BrowserBookmarksPage.java
index 1410ce8..ccacee8 100644
--- a/src/com/android/browser/BrowserBookmarksPage.java
+++ b/src/com/android/browser/BrowserBookmarksPage.java
@@ -16,6 +16,8 @@
 
 package com.android.browser;
 
+import com.android.browser.BreadCrumbView.Crumb;
+
 import android.app.Activity;
 import android.app.AlertDialog;
 import android.app.Fragment;
@@ -698,14 +700,18 @@
     }
 
     public boolean onBackPressed() {
-        if (mCrumbs != null &&
-                mCrumbs.size() > 0) {
+        if (canGoBack()) {
             mCrumbs.popView();
             return true;
         }
         return false;
     }
 
+    private boolean canGoBack() {
+        Crumb c = mCrumbs.getTopCrumb();
+        return c != null && c.canGoBack;
+    }
+
     public void setCallbackListener(BookmarksPageCallbacks callbackListener) {
         mCallbacks = callbackListener;
     }