Fixed bug where Uninstall dialog forces its own widget to close twice

Previously, ExtensionUninstallDialogViews called CloseNow() on it's own
delegate's Widget if it was destroyed before an Accept/Cancel handler
was called. However, the Widget had already been freed by the Widget
hierarchy, resulting in a crash.

Made ExtensionUninstallDialogViews notify
ExtensionUninstallDialogDelegateView when it closes, so now either order
is possible: either class can be destroyed first (either by the user, or
by the views hierarchy) and the other will be safely destroyed.

TEST=Open the App List in ChromeOS, then right-click on an app and
select 'App Info', then click 'Remove'. Now click away from the app list
to dismiss it. Previously, this would cause a crash.
TEST=Open the App List in Linux, then right-click on an app and
select 'App Info', then click 'Remove'. Now click the 'close' button in
the app info dialog to close the dismiss it. Previously, this would
cause a crash.

BUG=390414,400909

Review URL: https://codereview.chromium.org/412483006

Cr-Commit-Position: refs/heads/master@{#289227}
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@289227 0039d316-1c4b-4281-b951-d872f2087c98

chrome/browser/ui/views/extensions/extension_uninstall_dialog_view.cc

@@ -39,6 +39,10 @@ class ExtensionUninstallDialogViews
       extensions::ExtensionUninstallDialog::Delegate* delegate);
   virtual ~ExtensionUninstallDialogViews();
 
+  // Called when the ExtensionUninstallDialogDelegate has been destroyed to make
+  // sure we invalidate pointers.
+  void DialogDelegateDestroyed() { view_ = NULL; }
+
   // Forwards the accept and cancels to the delegate.
   void ExtensionUninstallAccepted();
   void ExtensionUninstallCanceled();
@@ -121,12 +125,14 @@ void ExtensionUninstallDialogViews::Show() {
 
 void ExtensionUninstallDialogViews::ExtensionUninstallAccepted() {
   // The widget gets destroyed when the dialog is accepted.
+  view_->DialogDestroyed();
   view_ = NULL;
   delegate_->ExtensionUninstallAccepted();
 }
 
 void ExtensionUninstallDialogViews::ExtensionUninstallCanceled() {
   // The widget gets destroyed when the dialog is canceled.
+  view_->DialogDestroyed();
   view_ = NULL;
   delegate_->ExtensionUninstallCanceled();
 }
@@ -154,6 +160,15 @@ ExtensionUninstallDialogDelegateView::ExtensionUninstallDialogDelegateView(
 }
 
 ExtensionUninstallDialogDelegateView::~ExtensionUninstallDialogDelegateView() {
+  // If we're here, 2 things could have happened. Either the user closed the
+  // dialog nicely and one of ExtensionUninstallAccepted or
+  // ExtensionUninstallCanceled has been called (in which case dialog_ will be
+  // NULL), *or* neither of them have been called and we are being forced closed
+  // by our parent widget. In this case, we need to make sure to notify dialog_
+  // not to call us again, since we're about to be freed by the Widget
+  // framework.
+  if (dialog_)
+    dialog_->DialogDelegateDestroyed();
 }
 
 base::string16 ExtensionUninstallDialogDelegateView::GetDialogButtonLabel(