Mojo: "Finish" local (in-process) implementation of data pipes.

Still to do:
- Write tests.
- Fix bug in MojoReadData()/MojoWriteData() (see data_pipe.cc).
- Write comments in core.h.

R=darin@chromium.org

Review URL: https://codereview.chromium.org/113603003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@241015 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 241015
Add BUILD.gn file for components's onc_component target.

BUG=None
TEST=gn, ninja -C out/Default onc_component
R=brettw@chromium.org

Review URL: https://codereview.chromium.org/111813003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@241016 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 241016