GMC: Always leave space for the dismiss button

This CL adds a new placeholder view to contain the dismiss button and
reserve space in the header so that nothing needs to shift when the
dismiss button shows or hides.

Bug: 1016369
Change-Id: Iaeb4f2735df814e5b8e29c79b28434f2aea1bb17
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1883622Reviewed-by: Jazz Xu <jazzhsu@chromium.org>
Commit-Queue: Tommy Steimel <steimel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#710037}

chrome/browser/ui/views/global_media_controls/media_notification_container_impl_view.cc

@@ -75,12 +75,19 @@ MediaNotificationContainerImplView::MediaNotificationContainerImplView(
   swipeable_container_->layer()->SetFillsBoundsOpaquely(false);
   AddChildView(swipeable_container_.get());
 
+  dismiss_button_placeholder_ = std::make_unique<views::View>();
+  dismiss_button_placeholder_->set_owned_by_client();
+  dismiss_button_placeholder_->SetPreferredSize(kDismissButtonSize);
+  dismiss_button_placeholder_->SetLayoutManager(
+      std::make_unique<views::FillLayout>());
+
   dismiss_button_container_ = std::make_unique<views::View>();
   dismiss_button_container_->set_owned_by_client();
   dismiss_button_container_->SetPreferredSize(kDismissButtonSize);
   dismiss_button_container_->SetLayoutManager(
       std::make_unique<views::FillLayout>());
   dismiss_button_container_->SetVisible(false);
+  dismiss_button_placeholder_->AddChildView(dismiss_button_container_.get());
 
   auto dismiss_button = std::make_unique<DismissButton>(this);
   dismiss_button->SetPreferredSize(kDismissButtonSize);
@@ -92,8 +99,8 @@ MediaNotificationContainerImplView::MediaNotificationContainerImplView(
   UpdateDismissButtonIcon();
 
   view_ = std::make_unique<media_message_center::MediaNotificationView>(
-      this, std::move(item), dismiss_button_container_.get(), base::string16(),
-      kWidth, /*should_show_icon=*/false);
+      this, std::move(item), dismiss_button_placeholder_.get(),
+      base::string16(), kWidth, /*should_show_icon=*/false);
   view_->set_owned_by_client();
   ForceExpandedState();
 

chrome/browser/ui/views/global_media_controls/media_notification_container_impl_view.h

@@ -100,7 +100,16 @@ class MediaNotificationContainerImplView
 
   const std::string id_;
   std::unique_ptr<views::View> swipeable_container_;
+
+  // Always "visible" so that it reserves space in the header so that the
+  // dismiss button can appear without forcing things to shift.
+  std::unique_ptr<views::View> dismiss_button_placeholder_;
+
+  // Shows the colored circle background behind the dismiss button to give it
+  // proper contrast against the artwork. The background can't be on the dismiss
+  // button itself because it messes up the ink drop.
   std::unique_ptr<views::View> dismiss_button_container_;
+
   DismissButton* dismiss_button_;
   std::unique_ptr<media_message_center::MediaNotificationView> view_;