media: Fix lifetime of InterfaceFactoryImpl and created impls

media/mojo/services/strong_binding_set.h

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef MEDIA_MOJO_SERVICES_STRONG_BINDING_SET_H_
+#define MEDIA_MOJO_SERVICES_STRONG_BINDING_SET_H_
+
+#include <map>
+#include <memory>
+#include <utility>
+
+#include "base/bind.h"
+#include "base/macros.h"
+#include "base/memory/ptr_util.h"
+#include "mojo/public/cpp/bindings/binding.h"
+#include "mojo/public/cpp/bindings/interface_request.h"
+
+namespace media {
+
+// This class manages a set of bindings. When the pipe a binding is bound to is
+// disconnected, the binding is automatically destroyed and removed from the
+// set, and the interface implementation is deleted. When the StrongBindingSet
+// is destructed, all outstanding bindings in the set are destroyed and all the
+// bound interface implementations are automatically deleted.
+template <typename Interface>
+class StrongBindingSet {
+ public:
+  using BindingId = size_t;
+  using RequestType = mojo::InterfaceRequest<Interface>;
+
+  StrongBindingSet() {}
+  ~StrongBindingSet() {}
+
+  // Adds a new binding to the set which binds |request| to |impl|.
+  BindingId AddBinding(std::unique_ptr<Interface> impl, RequestType request) {
+    BindingId binding_id = next_binding_id_++;
+    std::unique_ptr<Entry> entry = base::MakeUnique<Entry>(
+        std::move(impl), std::move(request), this, binding_id);
+    bindings_.insert(std::make_pair(binding_id, std::move(entry)));
+    return binding_id;
+  }
+
+  // Removes a binding from the set. Note that this is safe to call even if the
+  // binding corresponding to |binding_id| has already been removed.
+  // Returns |true| if the binding was removed and |false| if it didn't exist.
+  bool RemoveBinding(BindingId binding_id) {
+    auto it = bindings_.find(binding_id);
+    if (it == bindings_.end())
+      return false;
+    bindings_.erase(it);
+    return true;
+  }
+
+ private:
+  class Entry {
+   public:
+    Entry(std::unique_ptr<Interface> impl,
+          RequestType request,
+          StrongBindingSet* binding_set,
+          BindingId binding_id)
+        : impl_(std::move(impl)),
+          binding_(impl_.get(), std::move(request)),
+          binding_set_(binding_set),
+          binding_id_(binding_id) {
+      // base::Unretained() is safe because |this| is owned by the
+      // |binding_set|.
+      binding_.set_connection_error_with_reason_handler(
+          base::Bind(&StrongBindingSet::OnConnectionError,
+                     base::Unretained(binding_set), binding_id));
+    }
+
+    // Holds ownership of the interface implementation.
+    std::unique_ptr<Interface> impl_;
+
+    mojo::Binding<Interface> binding_;
+    StrongBindingSet* const binding_set_;
+    const BindingId binding_id_;
+
+    DISALLOW_COPY_AND_ASSIGN(Entry);
+  };
+
+  void OnConnectionError(BindingId binding_id,
+                         uint32_t custom_reason,
+                         const std::string& description) {
+    bool success = RemoveBinding(binding_id);
+    DCHECK(success) << "Binding for ID " << binding_id << " does not exist.";
+  }
+
+  std::map<BindingId, std::unique_ptr<Entry>> bindings_;
+  BindingId next_binding_id_ = 0;
+
+  DISALLOW_COPY_AND_ASSIGN(StrongBindingSet);
+};
+
+}  // namespace media
+
+#endif  // MEDIA_MOJO_SERVICES_STRONG_BINDING_SET_H_