Add multiplexing of message pipes in the new EDK.

mojo/edk/system/child_broker_host.h

Index: mojo/edk/system/child_broker_host.h
diff --git a/mojo/edk/system/child_broker_host.h b/mojo/edk/system/child_broker_host.h
index 7f4bc61e19db33cb60f4c700c0d6a67c7aeb654d..a91218ab8bfdcc9708c5c37a8d4225f8a94f5f61 100644
--- a/mojo/edk/system/child_broker_host.h
+++ b/mojo/edk/system/child_broker_host.h
@@ -8,20 +8,24 @@
 #include <vector>
 
 #include "base/compiler_specific.h"
+#include "base/macros.h"
 #include "base/message_loop/message_loop.h"
 #include "base/process/process_handle.h"
 #include "mojo/edk/embedder/scoped_platform_handle.h"
+#include "mojo/edk/system/raw_channel.h"
 #include "mojo/edk/system/system_impl_export.h"
 
 namespace mojo {
 namespace edk {
 
-// Responds to requests from a child process to exchange handles to tokens and
-// vice versa. There is one object of this class per child process host object.
+// Responds to requests from ChildBroker. This is used to handle message pipe
+// multiplexing and Windows sandbox messages. There is one object of this class
+// per child process host object.
 // This object will delete itself when it notices that the pipe is broken.
 class MOJO_SYSTEM_IMPL_EXPORT ChildBrokerHost
+    : public RawChannel::Delegate
 #if defined(OS_WIN)
-    : NON_EXPORTED_BASE(public base::MessageLoopForIO::IOHandler) {
+      , NON_EXPORTED_BASE(public base::MessageLoopForIO::IOHandler) {
 #else
     {
 #endif
@@ -33,17 +37,29 @@ class MOJO_SYSTEM_IMPL_EXPORT ChildBrokerHost
   // this class.
   ChildBrokerHost(base::ProcessHandle child_process, ScopedPlatformHandle pipe);
 
+  base::ProcessId GetProcessId();
+
+  // Sends a message to the child process to connect to |process_id| via |pipe|.
+  void ConnectToProcess(base::ProcessId process_id, ScopedPlatformHandle pipe);
+
+  // Sends a message to the child process that |pipe_id|'s other end is in
+  // |process_id|.
+  void ConnectMessagePipe(uint64_t pipe_id, base::ProcessId process_id);
+
  private:
-#if defined(OS_WIN)
   ~ChildBrokerHost() override;
-#else
-  ~ChildBrokerHost();
-#endif
 
+  // RawChannel::Delegate implementation:
+  void OnReadMessage(
+      const MessageInTransit::View& message_view,
+      ScopedPlatformHandleVectorPtr platform_handles) override;
+  void OnError(Error error) override;
+
+#if defined(OS_WIN)
   void RegisterIOHandler();
   void BeginRead();
 
-#if defined(OS_WIN)
+  // base::MessageLoopForIO::IOHandler implementation:
   void OnIOCompleted(base::MessageLoopForIO::IOContext* context,
                      DWORD bytes_transferred,
                      DWORD error) override;
@@ -53,18 +69,29 @@ class MOJO_SYSTEM_IMPL_EXPORT ChildBrokerHost
   HANDLE DuplicateFromChild(HANDLE handle);
 #endif
 
-  base::ProcessHandle child_process_;
-  ScopedPlatformHandle pipe_;
+  base::ProcessId process_id_;
+
+  // Channel used to receive and send multiplexing related messages.
+  RawChannel* child_channel_;
 
 #if defined(OS_WIN)
+  // Handle to the child process, used for duplication of handles.
+  base::ProcessHandle child_process_;
+
+  // Pipe used for synchronous messages from the child. Responses are written to
+  // it as well.
+  ScopedPlatformHandle sync_channel_;
+
   base::MessageLoopForIO::IOContext read_context_;
   base::MessageLoopForIO::IOContext write_context_;
-#endif
 
   std::vector<char> read_data_;
   // How many bytes in read_data_ we already read.
   uint32_t num_bytes_read_;
   std::vector<char> write_data_;
+#endif
+
+  DISALLOW_COPY_AND_ASSIGN(ChildBrokerHost);
 };
 
 }  // namespace edk