[Media Router] Fixed crash when showing dummy media notification.

This change also moves generation of the notification ID to the
notification item itself.

Bug: 1107164, b/161612881
Change-Id: Ie043c8810878ff357027076205f45b7f194da43c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2414311Reviewed-by: Elly Fong-Jones <ellyjones@chromium.org>
Commit-Queue: John Williams <jrw@chromium.org>
Cr-Commit-Position: refs/heads/master@{#807599}

chrome/browser/ui/global_media_controls/presentation_request_notification_item.cc

@@ -4,22 +4,19 @@
 
 #include "chrome/browser/ui/global_media_controls/presentation_request_notification_item.h"
 
-#include <utility>
-
+#include "base/unguessable_token.h"
 #include "chrome/browser/media/router/presentation/presentation_service_delegate_impl.h"
 #include "chrome/browser/ui/global_media_controls/media_notification_service.h"
 
 PresentationRequestNotificationItem::PresentationRequestNotificationItem(
-    const std::string& id,
     MediaNotificationService* notification_service,
     const content::PresentationRequest& request,
     std::unique_ptr<media_router::StartPresentationContext> context)
-    : id_(id),
+    : id_(base::UnguessableToken::Create().ToString()),
       notification_service_(notification_service),
       context_(std::move(context)) {
   // TODO(jrw): Save a copy of |request| once it is actually used.
   DCHECK(!context || request == context->presentation_request());
-  notification_service_->ShowNotification(id_);
 }
 
 PresentationRequestNotificationItem::~PresentationRequestNotificationItem() {

chrome/browser/ui/global_media_controls/presentation_request_notification_item.h

@@ -23,7 +23,6 @@ class PresentationRequestNotificationItem
     : public media_message_center::MediaNotificationItem {
  public:
   PresentationRequestNotificationItem(
-      const std::string& id,
       MediaNotificationService* notification_service,
       const content::PresentationRequest& request,
       std::unique_ptr<media_router::StartPresentationContext> context);

chrome/browser/ui/global_media_controls/presentation_request_notification_provider.cc

@@ -6,7 +6,6 @@
 
 #include <utility>
 
-#include "base/unguessable_token.h"
 #include "chrome/browser/media/router/media_router.h"
 #include "chrome/browser/media/router/media_router_factory.h"
 #include "chrome/browser/media/router/presentation/presentation_service_delegate_impl.h"
@@ -137,6 +136,6 @@ void PresentationRequestNotificationProvider::CreateItemForPresentationRequest(
     std::unique_ptr<media_router::StartPresentationContext> context) {
   // This may replace an existing item, which is the right thing to do if we've
   // reached this point.
-  item_.emplace(base::UnguessableToken().ToString(), notification_service_,
-                request, std::move(context));
+  item_.emplace(notification_service_, request, std::move(context));
+  notification_service_->ShowNotification(item_->id());
 }