Adds BrowserAssociatedInterface

BrowserAssociatedInterface can be implemented in conjunction with
BrowserMessageFilter in order to provide browser-side Mojo bindings
which dispatch on the IO thread and maintain FIFO with respect
to legacy IPC messages on the same channel.

BUG=612500,619202
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_site_isolation

Review-Url: https://codereview.chromium.org/2164783005
Cr-Commit-Position: refs/heads/master@{#407644}
10 files changed