Reify view ownership as a message pipe.

services/ui/view_manager/view_registry.h

Index: services/ui/view_manager/view_registry.h
diff --git a/services/ui/view_manager/view_registry.h b/services/ui/view_manager/view_registry.h
index c0562093b4cda5a11c15539da5b31406a0dbbc8d..3f2b7baf63e95286fd3896cb8a68912fd6779bdd 100644
--- a/services/ui/view_manager/view_registry.h
+++ b/services/ui/view_manager/view_registry.h
@@ -5,6 +5,7 @@
 #ifndef SERVICES_UI_VIEW_MANAGER_VIEW_REGISTRY_H_
 #define SERVICES_UI_VIEW_MANAGER_VIEW_REGISTRY_H_
 
+#include <string>
 #include <unordered_map>
 
 #include "base/macros.h"
@@ -15,6 +16,7 @@
 #include "services/ui/view_manager/view_associate_table.h"
 #include "services/ui/view_manager/view_layout_request.h"
 #include "services/ui/view_manager/view_state.h"
+#include "services/ui/view_manager/view_stub.h"
 #include "services/ui/view_manager/view_tree_state.h"
 
 namespace view_manager {
@@ -40,17 +42,22 @@ class ViewRegistry : public mojo::ui::ViewInspector {
   // VIEW MANAGER REQUESTS
 
   // Registers a view and returns its ViewToken.
-  mojo::ui::ViewTokenPtr RegisterView(
+  void RegisterView(
       mojo::ui::ViewPtr view,
       mojo::InterfaceRequest<mojo::ui::ViewHost> view_host_request,
+      mojo::InterfaceRequest<mojo::ui::ViewOwner> view_owner_request,
       const mojo::String& label);
 
   // Registers a view tree.
-  mojo::ui::ViewTreeTokenPtr RegisterViewTree(
+  void RegisterViewTree(
       mojo::ui::ViewTreePtr view_tree,
       mojo::InterfaceRequest<mojo::ui::ViewTreeHost> view_tree_host_request,
       const mojo::String& label);
 
+  // VIEW STUB REQUESTS
+
+  void OnViewResolved(ViewStub* view_stub, mojo::ui::ViewTokenPtr view_token);
+
   // VIEW HOST REQUESTS
 
   // Creates a scene for the view, replacing its current scene.
@@ -66,11 +73,14 @@ class ViewRegistry : public mojo::ui::ViewInspector {
   // Destroys |parent_state| if an error occurs.
   void AddChild(ViewState* parent_state,
                 uint32_t child_key,
-                mojo::ui::ViewTokenPtr child_view_token);
+                mojo::ui::ViewOwnerPtr child_view_owner);
 
   // Removes a child.
   // Destroys |parent_state| if an error occurs.
-  void RemoveChild(ViewState* parent_state, uint32_t child_key);
+  void RemoveChild(ViewState* parent_state,
+                   uint32_t child_key,
+                   mojo::InterfaceRequest<mojo::ui::ViewOwner>
+                       transferred_view_owner_request);
 
   // Lays out a child and optionally provides its size.
   // Destroys |parent_state| if an error occurs.
@@ -85,6 +95,9 @@ class ViewRegistry : public mojo::ui::ViewInspector {
                             const mojo::String& service_name,
                             mojo::ScopedMessagePipeHandle client_handle);
 
+  // Called when one of the view pipes is closed remotely.
+  void OnViewDied(ViewState* view_state, const std::string& reason);
+
   // VIEW TREE HOST REQUESTS
 
   // Requests layout.
@@ -95,11 +108,13 @@ class ViewRegistry : public mojo::ui::ViewInspector {
   // Destroys |tree_state| if an error occurs.
   void SetRoot(ViewTreeState* tree_state,
                uint32_t root_key,
-               mojo::ui::ViewTokenPtr root_view_token);
+               mojo::ui::ViewOwnerPtr root_view_owner);
 
   // Resets the root of the view tree.
   // Destroys |tree_state| if an error occurs.
-  void ResetRoot(ViewTreeState* tree_state);
+  void ResetRoot(ViewTreeState* tree_state,
+                 mojo::InterfaceRequest<mojo::ui::ViewOwner>
+                     transferred_view_owner_request);
 
   // Lays out a view tree's root and optionally provides its size.
   // Destroys |tree_state| if an error occurs.
@@ -113,48 +128,45 @@ class ViewRegistry : public mojo::ui::ViewInspector {
                                 const mojo::String& service_name,
                                 mojo::ScopedMessagePipeHandle client_handle);
 
+  // Called when one of the view tree pipes is closed remotely.
+  void OnViewTreeDied(ViewTreeState* tree_state, const std::string& reason);
+
  private:
   // LIFETIME
 
-  void OnViewConnectionError(ViewState* view_state);
   void UnregisterView(ViewState* view_state);
-  void OnViewTreeConnectionError(ViewTreeState* tree_state);
   void UnregisterViewTree(ViewTreeState* tree_state);
 
   // TREE MANIPULATION
 
   ViewState* FindView(uint32_t view_token_value);
-  void LinkChild(ViewState* parent_state,
-                 uint32_t child_key,
-                 ViewState* child_state);
-  void LinkChildAsUnavailable(ViewState* parent_state, uint32_t child_key);
-  void MarkChildAsUnavailable(ViewState* parent_state, uint32_t child_key);
-  void UnlinkChild(ViewState* parent_state,
-                   ViewState::ChildrenMap::iterator child_it);
-
   ViewTreeState* FindViewTree(uint32_t view_tree_token_value);
-  void LinkRoot(ViewTreeState* tree_state,
-                ViewState* root_state,
-                uint32_t root_key);
-  void UnlinkRoot(ViewTreeState* tree_state);
+
   void HijackView(ViewState* view_state);
 
-  // Must be called before the view is actually unlinked from the tree.
-  // Caller is still responsible for actually unlinking the view.
-  void ResetStateWhenUnlinking(ViewState* view_state);
+  void AttachViewStubAndNotify(ViewStub* view_stub, ViewState* view_state);
+  void ReleaseViewStubAndNotify(ViewStub* view_stub);
+  void TransferOrUnregisterViewStub(std::unique_ptr<ViewStub> view_stub,
+                                    mojo::InterfaceRequest<mojo::ui::ViewOwner>
+                                        transferred_view_owner_request);
+  void UnregisterViewStub(std::unique_ptr<ViewStub> view_stub);
 
   // LAYOUT
 
-  void InvalidateLayout(ViewState* view_state);
-  void InvalidateLayoutForChild(ViewState* parent_state, uint32_t child_key);
-  void InvalidateLayoutForRoot(ViewTreeState* tree_state);
-  void SetLayout(ViewState* view_state,
+  void SetLayout(ViewStub* view_stub,
                  mojo::ui::ViewLayoutParamsPtr layout_params,
                  const ViewLayoutCallback& callback);
   void EnqueueLayoutRequest(ViewState* view_state,
                             mojo::ui::ViewLayoutParamsPtr layout_params);
+  void InvalidateLayout(ViewState* view_state);
+  void InvalidateLayoutForChild(ViewState* parent_state, uint32_t child_key);
+  void InvalidateLayoutForRoot(ViewTreeState* tree_state);
+
   void IssueNextViewLayoutRequest(ViewState* view_state);
   void IssueNextViewTreeLayoutRequest(ViewTreeState* tree_state);
+  void OnViewLayoutResult(base::WeakPtr<ViewState> view_state_weak,
+                          mojo::ui::ViewLayoutResultPtr result);
+  void OnViewTreeLayoutResult(base::WeakPtr<ViewTreeState> tree_state_weak);
 
   // SCENE MANAGEMENT
 
@@ -165,11 +177,6 @@ class ViewRegistry : public mojo::ui::ViewInspector {
 
   void SendChildUnavailable(ViewState* parent_state, uint32_t child_key);
   void SendRootUnavailable(ViewTreeState* tree_state, uint32_t root_key);
-  void SendViewLayoutRequest(ViewState* view_state);
-  void SendViewTreeLayoutRequest(ViewTreeState* tree_state);
-  void OnViewLayoutResult(base::WeakPtr<ViewState> view_state_weak,
-                          mojo::ui::ViewLayoutResultPtr result);
-  void OnViewTreeLayoutResult(base::WeakPtr<ViewTreeState> tree_state_weak);
 
   bool IsViewStateRegisteredDebug(ViewState* view_state) {
     return view_state && FindView(view_state->view_token()->value);