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 ac09c5ab1ef1d00b31c4f3a2e7b0a260673dbfbe..89505cb5f76e40ebae0075197c95b3199a0f7fbf 100644
--- a/ipc/ipc_channel.cc
+++ b/ipc/ipc_channel.cc
@@ -41,4 +41,26 @@ std::string Channel::GenerateUniqueRandomChannelID() {
       base::RandInt(0, std::numeric_limits<int32>::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_);
+}
+
+size_t Channel::OutputElement::size() const {
+  if (message_)

[Tom Sepez, 2015/09/10 15:41:05]

nit: I'd use the ? operator here and below, just because it all fits on one
line.  Also, do you want these in the header to aid in inlining?

[erikchen, 2015/09/10 18:43:59]

I switched to the ternary operator, and moved the code into the header.

+    return message_->size();
+  return length_;
+}
+
+const void* Channel::OutputElement::data() const {
+  if (message_)

[Tom Sepez, 2015/09/10 15:41:05]

do you want to assert that there isn't both message and buffer_?

[erikchen, 2015/09/10 18:43:59]

Given that that assertion is enforced by the constructor, the only way for both
message and buffer_ to exist is memory corruption, which is not something I'm
inclined to add assertions for.

+    return message_->data();
+  return buffer_;
+}
+
 }  // namespace IPC