Parent the AppInfoDialog using a ModalDialogHost

ui/app_list/views/contents_view.h

Index: ui/app_list/views/contents_view.h
diff --git a/ui/app_list/views/contents_view.h b/ui/app_list/views/contents_view.h
index 175d8326fd950e88ba8448f62b9518684e105268..e9e472de153ce458c255e337553495e869ff87de 100644
--- a/ui/app_list/views/contents_view.h
+++ b/ui/app_list/views/contents_view.h
@@ -12,6 +12,7 @@
 #include "base/compiler_specific.h"
 #include "base/memory/linked_ptr.h"
 #include "base/memory/scoped_ptr.h"
+#include "components/web_modal/modal_dialog_host.h"
 #include "ui/app_list/app_list_export.h"
 #include "ui/app_list/app_list_model.h"
 #include "ui/app_list/pagination_model.h"
@@ -44,7 +45,8 @@ class StartPageView;
 // interface for switching between launcher pages, and animates the transition
 // between them.
 class APP_LIST_EXPORT ContentsView : public views::View,
-                                     public PaginationModelObserver {
+                                     public PaginationModelObserver,
+                                     public web_modal::ModalDialogHost {
  public:
   ContentsView(AppListMainView* app_list_main_view);
   ~ContentsView() override;
@@ -131,6 +133,12 @@ class APP_LIST_EXPORT ContentsView : public views::View,
   void TransitionStarted() override;
   void TransitionChanged() override;
 
+  // Overridden from web_modal::ModalDialogHost:
+  gfx::NativeView GetHostView() const override;
+  gfx::Point GetDialogPosition(const gfx::Size& size) override;
+  void AddObserver(web_modal::ModalDialogHostObserver* observer) override;
+  void RemoveObserver(web_modal::ModalDialogHostObserver* observer) override;
+
  private:
   // Sets the active launcher page, accounting for whether the change is for
   // search results.