ipc: Add the inner class OutputElement to Channel.

ipc/ipc_channel.cc

Index: ipc/ipc_channel.cc
diff --git a/ipc/ipc_channel.cc b/ipc/ipc_channel.cc
index e659205ae6d290eab2b13aa07a270e3d56e6f335..6772e1c55794d1dec4b4df8392b07e73ca738e3e 100644
--- a/ipc/ipc_channel.cc
+++ b/ipc/ipc_channel.cc
@@ -43,4 +43,14 @@ std::string Channel::GenerateUniqueRandomChannelID() {
       base::RandInt(0, std::numeric_limits<int32_t>::max()));
 }
 
+Channel::OutputElement::OutputElement(Message* message)
+    : message_(message), buffer_(nullptr), length_(0) {}
+
+Channel::OutputElement::OutputElement(void* buffer, size_t length)
+    : message_(nullptr), buffer_(buffer), length_(length) {}
+
+Channel::OutputElement::~OutputElement() {
+  free(buffer_);
+}
+
 }  // namespace IPC