Presentation API: fix crash when unable to create a Fragment for the dialog.

chrome/android/java/src/org/chromium/chrome/browser/media/router/BaseMediaRouteDialogManager.java

Index: chrome/android/java/src/org/chromium/chrome/browser/media/router/BaseMediaRouteDialogManager.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/media/router/BaseMediaRouteDialogManager.java b/chrome/android/java/src/org/chromium/chrome/browser/media/router/BaseMediaRouteDialogManager.java
index 284f18dc5aeb6b224e370ae6532f129a1d4a7a96..a6d5a7e9c931de185d09bb05150204efb582c52e 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/media/router/BaseMediaRouteDialogManager.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/media/router/BaseMediaRouteDialogManager.java
@@ -6,9 +6,12 @@ package org.chromium.chrome.browser.media.router;
 
 import android.app.Activity;
 import android.content.Context;
+import android.content.DialogInterface;
+import android.os.Handler;
 import android.support.v4.app.DialogFragment;
 import android.support.v4.app.FragmentActivity;
 import android.support.v4.app.FragmentManager;
+import android.support.v7.app.MediaRouteChooserDialogFragment;
 import android.support.v7.media.MediaRouter;
 import android.view.View;
 import android.widget.FrameLayout;
@@ -111,6 +114,51 @@ public abstract class BaseMediaRouteDialogManager implements MediaRouteDialogMan
     }
 
     /**
+     * Base class for media router dialog fragment. Classes inheriting from
+     * BaseMediaRouteDialogManager may extend the implementation but must redirect the empty
+     * constructor to this implementation to handle the case of the Fragment being created via
+     * this method.
+     */
+    public static class Fragment extends MediaRouteChooserDialogFragment {
+        private final Handler mHandler = new Handler();
+        private final SystemVisibilitySaver mVisibilitySaver = new SystemVisibilitySaver();
+        protected BaseMediaRouteDialogManager mManager = null;
+
+        public Fragment() {
+            mHandler.post(new Runnable() {
+                @Override
+                public void run() {
+                    Fragment.this.dismiss();
+                }
+            });
+        }
+
+        public Fragment(BaseMediaRouteDialogManager manager) {
+            mManager = manager;
+        }
+
+        @Override
+        public void onStart() {
+            mVisibilitySaver.saveSystemVisibility(getActivity());
+            super.onStart();
+        }
+
+        @Override
+        public void onStop() {
+            super.onStop();
+            mVisibilitySaver.restoreSystemVisibility(getActivity());
+        }
+
+        @Override
+        public void onDismiss(DialogInterface dialog) {
+            super.onDismiss(dialog);
+            if (mManager == null) return;
+
+            mManager.mDialogFragment = null;
+        }
+    }
+
+    /**
      * Initializes and shows the {@link DialogFragment} instance corresponding to the dialog type
      * needed.
      *