Support early associated interface binding on ChannelMojo

ipc/ipc_message_pipe_reader.h

Index: ipc/ipc_message_pipe_reader.h
diff --git a/ipc/ipc_message_pipe_reader.h b/ipc/ipc_message_pipe_reader.h
index 5aec4407aaef45842c397d4402e846ba9f4dbd8c..e6a2a137a0a39930266c1400977befb13d10c51a 100644
--- a/ipc/ipc_message_pipe_reader.h
+++ b/ipc/ipc_message_pipe_reader.h
@@ -13,6 +13,7 @@
 #include "base/atomicops.h"
 #include "base/compiler_specific.h"
 #include "base/macros.h"
+#include "base/process/process_handle.h"
 #include "base/threading/thread_checker.h"
 #include "ipc/ipc.mojom.h"
 #include "ipc/ipc_export.h"
@@ -47,6 +48,7 @@ class IPC_EXPORT MessagePipeReader : public NON_EXPORTED_BASE(mojom::Channel) {
  public:
   class Delegate {
    public:
+    virtual void OnPeerPidReceived() = 0;
     virtual void OnMessageReceived(const Message& message) = 0;
     virtual void OnPipeError() = 0;
     virtual void OnAssociatedInterfaceRequest(
@@ -54,21 +56,6 @@ class IPC_EXPORT MessagePipeReader : public NON_EXPORTED_BASE(mojom::Channel) {
         mojo::ScopedInterfaceEndpointHandle handle) = 0;
   };
 
-  // Delay the object deletion using the current message loop.
-  // This is intended to used by MessagePipeReader owners.
-  class DelayedDeleter {
-   public:
-    typedef std::default_delete<MessagePipeReader> DefaultType;
-
-    static void DeleteNow(MessagePipeReader* ptr) { delete ptr; }
-
-    DelayedDeleter() {}
-    explicit DelayedDeleter(const DefaultType&) {}
-    DelayedDeleter& operator=(const DefaultType&) { return *this; }
-
-    void operator()(MessagePipeReader* ptr) const;
-  };
-
   // Builds a reader that reads messages from |receive_handle| and lets
   // |delegate| know.
   //
@@ -82,7 +69,6 @@ class IPC_EXPORT MessagePipeReader : public NON_EXPORTED_BASE(mojom::Channel) {
   MessagePipeReader(mojo::MessagePipeHandle pipe,
                     mojom::ChannelAssociatedPtr sender,
                     mojo::AssociatedInterfaceRequest<mojom::Channel> receiver,
-                    base::ProcessId peer_pid,
                     Delegate* delegate);
   ~MessagePipeReader() override;
 
@@ -108,6 +94,7 @@ class IPC_EXPORT MessagePipeReader : public NON_EXPORTED_BASE(mojom::Channel) {
 
  private:
   // mojom::Channel:
+  void SetPeerPid(int32_t peer_pid) override;
   void Receive(mojo::Array<uint8_t> data,
                mojo::Array<mojom::SerializedHandlePtr> handles) override;
   void GetAssociatedInterface(
@@ -116,7 +103,7 @@ class IPC_EXPORT MessagePipeReader : public NON_EXPORTED_BASE(mojom::Channel) {
 
   // |delegate_| is null once the message pipe is closed.
   Delegate* delegate_;
-  base::ProcessId peer_pid_;
+  base::ProcessId peer_pid_ = base::kNullProcessId;
   mojom::ChannelAssociatedPtr sender_;
   mojo::AssociatedBinding<mojom::Channel> binding_;