Initialize IPC:ChannelHandle from existing HANDLE

ipc/ipc_channel_win.cc

Index: ipc/ipc_channel_win.cc
diff --git a/ipc/ipc_channel_win.cc b/ipc/ipc_channel_win.cc
index cd313d21a96fbd83af6189696ba60960091d8870..047690e30c72c9dc622e92a028ecf1ee6ed8cb2e 100644
--- a/ipc/ipc_channel_win.cc
+++ b/ipc/ipc_channel_win.cc
@@ -115,16 +115,25 @@ bool Channel::ChannelImpl::CreatePipe(const IPC::ChannelHandle &channel_handle,
                                       Mode mode) {
   DCHECK_EQ(INVALID_HANDLE_VALUE, pipe_);
   const std::wstring pipe_name = PipeName(channel_handle.name);
-  if (mode & MODE_SERVER_FLAG) {
+  // If we already have a valid pipe for channel just copy it.
+  if (channel_handle.pipe.IsValid()) {
+    DuplicateHandle(GetCurrentProcess(),
+                    channel_handle.pipe,
+                    GetCurrentProcess(),
+                    &pipe_,
+                    0,
+                    FALSE,
+                    DUPLICATE_SAME_ACCESS);
+  } else if (mode & MODE_SERVER_FLAG) {
     pipe_ = CreateNamedPipeW(pipe_name.c_str(),
-                             PIPE_ACCESS_DUPLEX | FILE_FLAG_OVERLAPPED |
+                              PIPE_ACCESS_DUPLEX | FILE_FLAG_OVERLAPPED |
                               FILE_FLAG_FIRST_PIPE_INSTANCE,
-                             PIPE_TYPE_BYTE | PIPE_READMODE_BYTE,
-                             1,
-                             Channel::kReadBufferSize,
-                             Channel::kReadBufferSize,
-                             5000,
-                             NULL);
+                              PIPE_TYPE_BYTE | PIPE_READMODE_BYTE,
+                              1,
+                              Channel::kReadBufferSize,
+                              Channel::kReadBufferSize,
+                              5000,
+                              NULL);
   } else if (mode & MODE_CLIENT_FLAG) {
     pipe_ = CreateFileW(pipe_name.c_str(),
                         GENERIC_READ | GENERIC_WRITE,
@@ -137,6 +146,7 @@ bool Channel::ChannelImpl::CreatePipe(const IPC::ChannelHandle &channel_handle,
   } else {
     NOTREACHED();
   }
+
   if (pipe_ == INVALID_HANDLE_VALUE) {
     // If this process is being closed, the pipe may be gone already.
     LOG(WARNING) << "Unable to create pipe \"" << pipe_name <<