Mojo C++ bindings: Simplify associated interface API.

mojo/public/cpp/bindings/associated_group.h

Index: mojo/public/cpp/bindings/associated_group.h
diff --git a/mojo/public/cpp/bindings/associated_group.h b/mojo/public/cpp/bindings/associated_group.h
index b1c692acd2393cb4052cf33747863122078e28dc..21d6fcbf2dde4452ce1c90ce8898b42dd0dbca3a 100644
--- a/mojo/public/cpp/bindings/associated_group.h
+++ b/mojo/public/cpp/bindings/associated_group.h
@@ -5,8 +5,7 @@
 #ifndef MOJO_PUBLIC_CPP_BINDINGS_ASSOCIATED_GROUP_H_
 #define MOJO_PUBLIC_CPP_BINDINGS_ASSOCIATED_GROUP_H_
 
-#include <utility>
-
+#include "base/callback.h"
 #include "base/memory/ref_counted.h"
 #include "mojo/public/cpp/bindings/associated_interface_ptr_info.h"
 #include "mojo/public/cpp/bindings/associated_interface_request.h"
@@ -18,22 +17,37 @@ namespace mojo {
 class AssociatedGroupController;
 
 // AssociatedGroup refers to all the interface endpoints running at one end of a
-// message pipe. It is used to create associated interfaces for that message
-// pipe.
+// message pipe.
 // It is thread safe and cheap to make copies.
 class MOJO_CPP_BINDINGS_EXPORT AssociatedGroup {
  public:
-  // Configuration used by CreateAssociatedInterface(). Please see the comments
-  // of that method for more details.
-  enum AssociatedInterfaceConfig { WILL_PASS_PTR, WILL_PASS_REQUEST };
-
   AssociatedGroup();
+
+  explicit AssociatedGroup(scoped_refptr<AssociatedGroupController> controller);
+
+  explicit AssociatedGroup(const ScopedInterfaceEndpointHandle& handle);
+
   AssociatedGroup(const AssociatedGroup& other);
 
   ~AssociatedGroup();
 
   AssociatedGroup& operator=(const AssociatedGroup& other);
 
+  // The return value of this getter if this object is initialized with a
+  // ScopedInterfaceEndpointHandle:
+  //   - If the handle is invalid, the return value will always be null.
+  //   - If the handle is valid and non-pending, the return value will be
+  //     non-null and remain unchanged even if the handle is later reset.
+  //   - If the handle is pending asssociation, the return value will initially
+  //     be null, change to non-null when/if the handle is associated, and
+  //     remain unchanged ever since.
+  AssociatedGroupController* GetController();
+
+  // TODO(yzshen): Remove the following public method. It is not needed anymore.
+  // Configuration used by CreateAssociatedInterface(). Please see the comments
+  // of that method for more details.
+  enum AssociatedInterfaceConfig { WILL_PASS_PTR, WILL_PASS_REQUEST };
+
   // |config| indicates whether |ptr_info| or |request| will be sent to the
   // remote side of the message pipe.
   //
@@ -45,44 +59,30 @@ class MOJO_CPP_BINDINGS_EXPORT AssociatedGroup {
   // no need to wait until |request| is bound to an implementation at the remote
   // side.
   template <typename T>
-  void CreateAssociatedInterface(
-      AssociatedInterfaceConfig config,
-      AssociatedInterfacePtrInfo<T>* ptr_info,
-      AssociatedInterfaceRequest<T>* request) {
-    ScopedInterfaceEndpointHandle local;
-    ScopedInterfaceEndpointHandle remote;
-    CreateEndpointHandlePair(&local, &remote);
-
-    if (!local.is_valid() || !remote.is_valid()) {
-      *ptr_info = AssociatedInterfacePtrInfo<T>();
-      *request = AssociatedInterfaceRequest<T>();
-      return;
-    }
+  void CreateAssociatedInterface(AssociatedInterfaceConfig config,
+                                 AssociatedInterfacePtrInfo<T>* ptr_info,
+                                 AssociatedInterfaceRequest<T>* request) {
+    ScopedInterfaceEndpointHandle handle0;
+    ScopedInterfaceEndpointHandle handle1;
+    ScopedInterfaceEndpointHandle::CreatePairPendingAssociation(&handle0,
+                                                                &handle1);
 
-    if (config == WILL_PASS_PTR) {
-      ptr_info->set_handle(std::move(remote));
+    ptr_info->set_handle(std::move(handle0));
+    request->Bind(std::move(handle1));
 
+    if (config == WILL_PASS_PTR) {
       // The implementation is local, therefore set the version according to
       // the interface definition that this code is built against.
       ptr_info->set_version(T::Version_);
-      request->Bind(std::move(local));
     } else {
-      ptr_info->set_handle(std::move(local));
-
       // The implementation is remote, we don't know about its actual version
       // yet.
       ptr_info->set_version(0u);
-      request->Bind(std::move(remote));
     }
   }
 
  private:
-  friend class AssociatedGroupController;
-
-  void CreateEndpointHandlePair(
-      ScopedInterfaceEndpointHandle* local_endpoint,
-      ScopedInterfaceEndpointHandle* remote_endpoint);
-
+  base::Callback<AssociatedGroupController*()> controller_getter_;
   scoped_refptr<AssociatedGroupController> controller_;
 };