Remove PageInfo subpages when dialog is closed

To ensure that all fragments are removed when the PageInfo dialog is
closed, the subpage controller needs to be notified when the main
controller is dismissed.

Bug: 1152724
Change-Id: I075a214223ceee675578615226b958880a103946
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2560628Reviewed-by: Ehimare Okoyomon <eokoyomon@chromium.org>
Commit-Queue: Christian Dullweber <dullweber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#831024}

components/page_info/android/java/src/org/chromium/components/page_info/PageInfoController.java

@@ -488,6 +488,10 @@ public class PageInfoController implements PageInfoMainController, ModalDialogPr
             mPendingRunAfterDismissTask.run();
             mPendingRunAfterDismissTask = null;
         }
+        if (mSubpageController != null) {
+            mSubpageController.onSubpageRemoved();
+            mSubpageController = null;
+        }
         mWebContentsObserver.destroy();
         mWebContentsObserver = null;
         PageInfoControllerJni.get().destroy(mNativePageInfoController, PageInfoController.this);