ash: Fix race condition around Surface finding

exo::Surface might be unavailable when:
- Just after the Activity starts
- It's getting recreated when resizing the window.

BUG=925769
TEST=manually

Change-Id: Ie6dbf9349aeec6f65366fb3d1f077135c0439dd8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1493689Reviewed-by: Mitsuru Oshima <oshima@chromium.org>
Commit-Queue: Ryo Hashimoto <hashimoto@chromium.org>
Cr-Commit-Position: refs/heads/master@{#649741}

ash/custom_tab/arc_custom_tab_view.cc

@@ -72,7 +72,7 @@ mojom::ArcCustomTabViewPtr ArcCustomTabView::Create(int32_t task_id,
     return nullptr;
   }
   auto* parent = widget->widget_delegate()->GetContentsView();
-  auto* view = new ArcCustomTabView(surface_id, top_margin);
+  auto* view = new ArcCustomTabView(arc_app_window, surface_id, top_margin);
   parent->AddChildView(view);
   parent->SetLayoutManager(std::make_unique<views::FillLayout>());
   parent->Layout();
@@ -118,17 +118,32 @@ void ArcCustomTabView::Layout() {
   window->parent()->StackChildAtTop(window);
 }
 
-ArcCustomTabView::ArcCustomTabView(int32_t surface_id, int32_t top_margin)
+void ArcCustomTabView::OnWindowHierarchyChanged(
+    const HierarchyChangeParams& params) {
+  auto* surface = exo::Surface::AsSurface(params.target);
+  if (surface && surface->GetClientSurfaceId() == surface_id_ &&
+      params.new_parent != nullptr) {
+    Layout();
+  }
+}
+
+ArcCustomTabView::ArcCustomTabView(aura::Window* arc_app_window,
+                                   int32_t surface_id,
+                                   int32_t top_margin)
     : binding_(this),
       remote_view_host_(new ws::ServerRemoteViewHost(
           ash::Shell::Get()->window_service_owner()->window_service())),
+      arc_app_window_(arc_app_window),
       surface_id_(surface_id),
       top_margin_(top_margin),
       weak_ptr_factory_(this) {
   AddChildView(remote_view_host_);
+  arc_app_window_->AddObserver(this);
 }
 
-ArcCustomTabView::~ArcCustomTabView() = default;
+ArcCustomTabView::~ArcCustomTabView() {
+  arc_app_window_->RemoveObserver(this);
+}
 
 void ArcCustomTabView::Bind(mojom::ArcCustomTabViewPtr* ptr) {
   binding_.Bind(mojo::MakeRequest(ptr));

ash/custom_tab/arc_custom_tab_view.h

@@ -11,12 +11,15 @@
 #include "base/macros.h"
 #include "mojo/public/cpp/bindings/binding.h"
 #include "services/ws/remote_view_host/server_remote_view_host.h"
+#include "ui/aura/window_observer.h"
 #include "ui/views/view.h"
 
 namespace ash {
 
 // Implementation of ArcCustomTabView interface.
-class ArcCustomTabView : public views::View, public mojom::ArcCustomTabView {
+class ArcCustomTabView : public views::View,
+                         public mojom::ArcCustomTabView,
+                         public aura::WindowObserver {
  public:
   // Creates a new ArcCustomTabView instance. The instance will be deleted when
   // the pointer is closed. Returns null when the arguments are invalid.
@@ -30,8 +33,13 @@ class ArcCustomTabView : public views::View, public mojom::ArcCustomTabView {
   // views::View:
   void Layout() override;
 
+  // aura::WindowObserver:
+  void OnWindowHierarchyChanged(const HierarchyChangeParams& params) override;
+
  private:
-  ArcCustomTabView(int32_t surface_id, int32_t top_margin);
+  ArcCustomTabView(aura::Window* arc_app_window,
+                   int32_t surface_id,
+                   int32_t top_margin);
   ~ArcCustomTabView() override;
 
   // Binds this instance to the pointer.
@@ -45,6 +53,7 @@ class ArcCustomTabView : public views::View, public mojom::ArcCustomTabView {
 
   mojo::Binding<mojom::ArcCustomTabView> binding_;
   ws::ServerRemoteViewHost* remote_view_host_;
+  aura::Window* arc_app_window_;
   int32_t surface_id_, top_margin_;
   base::WeakPtrFactory<ArcCustomTabView> weak_ptr_factory_;