[Cast,Android] Subscribe to onCancel and onDismiss correctly

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

Index: chrome/android/java/src/org/chromium/chrome/browser/media/router/ChromeMediaRouterDialogController.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/media/router/ChromeMediaRouterDialogController.java b/chrome/android/java/src/org/chromium/chrome/browser/media/router/ChromeMediaRouterDialogController.java
index d294354e0a2e2391eaf9fd3502570cdf53e22079..4d21c7d96e49e573d48db8865f04a9d5ceebdca2 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/media/router/ChromeMediaRouterDialogController.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/media/router/ChromeMediaRouterDialogController.java
@@ -104,6 +104,12 @@ public class ChromeMediaRouterDialogController implements MediaRouteDialogDelega
 
     @Override
     public void onDialogCancelled() {
+        // For MediaRouteControllerDialog this method will be called in case the route is closed
+        // since it only call onDismiss() and there's no way to distinguish between the two.
+        // Here we can figure it out: if mDialogManager is null, onRouteClosed() was called and
+        // there's no need to tell the native controller the dialog has been cancelled.
+        if (mDialogManager == null) return;
+
         mDialogManager = null;
         nativeOnDialogCancelled(mNativeDialogController);
     }