Add support to be able to asynchronously read from a CancelableSyncSocket

Add support to be able to asynchronously read from a CancelableSyncSocket
on a TYPE_IO message loop thread.  This makes it easy to share a thread
that uses a message loop (e.g. for IPC and other things) and not require
a separate thread to read from the socket.

TEST=Run media_unittests. (--gtest_filter=AsyncSocketIoHandlerTest.*)

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=140994

[henrika (OOO until Aug 14), 2012-06-07 12:25:48]

Amazing stuff. Did not dig into the details at this stage. Mainly nits.
LGTM.

[henrika (OOO until Aug 14), 2012-06-07 12:25:59]

https://chromiumcodereview.appspot.com/10540047/diff/1/media/audio/async_sock...
File media/audio/async_socket_io_handler.h (right):

https://chromiumcodereview.appspot.com/10540047/diff/1/media/audio/async_sock...
media/audio/async_socket_io_handler.h:76: // Private implementation.
Remove comment?

https://chromiumcodereview.appspot.com/10540047/diff/1/media/audio/async_sock...
media/audio/async_socket_io_handler.h:91: // Member variables.
Needed?

https://chromiumcodereview.appspot.com/10540047/diff/1/media/audio/async_sock...
File media/audio/async_socket_io_handler_posix.cc (right):

https://chromiumcodereview.appspot.com/10540047/diff/1/media/audio/async_sock...
media/audio/async_socket_io_handler_posix.cc:25: pending_buffer_len_));
nit, fix indentation

https://chromiumcodereview.appspot.com/10540047/diff/1/media/audio/async_sock...
media/audio/async_socket_io_handler_posix.cc:39: const ReadCompleteCallback&
callback) {
odd indentation

https://chromiumcodereview.appspot.com/10540047/diff/1/media/audio/async_sock...
File media/audio/async_socket_io_handler_win.cc (right):

https://chromiumcodereview.appspot.com/10540047/diff/1/media/audio/async_sock...
media/audio/async_socket_io_handler_win.cc:50: &context_->overlapped);
fix indentation

https://chromiumcodereview.appspot.com/10540047/diff/1/media/audio/async_sock...
media/audio/async_socket_io_handler_win.cc:54: // The completion port will be
signaled regardless of completing the read
Odd place to place a comment.

[tommi (sloooow) - chröme, 2012-06-07 12:34:33]

https://chromiumcodereview.appspot.com/10540047/diff/1/media/audio/async_sock...
File media/audio/async_socket_io_handler.h (right):

https://chromiumcodereview.appspot.com/10540047/diff/1/media/audio/async_sock...
media/audio/async_socket_io_handler.h:76: // Private implementation.
On 2012/06/07 12:25:59, henrika wrote:
> Remove comment?

Done.

https://chromiumcodereview.appspot.com/10540047/diff/1/media/audio/async_sock...
media/audio/async_socket_io_handler.h:91: // Member variables.
On 2012/06/07 12:25:59, henrika wrote:
> Needed?

Done.

https://chromiumcodereview.appspot.com/10540047/diff/1/media/audio/async_sock...
File media/audio/async_socket_io_handler_posix.cc (right):

https://chromiumcodereview.appspot.com/10540047/diff/1/media/audio/async_sock...
media/audio/async_socket_io_handler_posix.cc:25: pending_buffer_len_));
On 2012/06/07 12:25:59, henrika wrote:
> nit, fix indentation

Done.

https://chromiumcodereview.appspot.com/10540047/diff/1/media/audio/async_sock...
media/audio/async_socket_io_handler_posix.cc:39: const ReadCompleteCallback&
callback) {
On 2012/06/07 12:25:59, henrika wrote:
> odd indentation

Done.

https://chromiumcodereview.appspot.com/10540047/diff/1/media/audio/async_sock...
File media/audio/async_socket_io_handler_win.cc (right):

https://chromiumcodereview.appspot.com/10540047/diff/1/media/audio/async_sock...
media/audio/async_socket_io_handler_win.cc:50: &context_->overlapped);
On 2012/06/07 12:25:59, henrika wrote:
> fix indentation

Done.

https://chromiumcodereview.appspot.com/10540047/diff/1/media/audio/async_sock...
media/audio/async_socket_io_handler_win.cc:54: // The completion port will be
signaled regardless of completing the read
On 2012/06/07 12:25:59, henrika wrote:
> Odd place to place a comment.

Done. Also improved the comment.