Let IPC::SyncMessageFilter take advantage of thread-safe Send.

SyncMessageFilter is unnecessarily hopping to the IO thread
before writing to its underlying Sender when the underlying
Sender has a thread-safe Send implementation.

This fixes that.

BUG=516464

Review URL: https://codereview.chromium.org/1262253004

Cr-Commit-Position: refs/heads/master@{#342027}


CrOS-Libchrome-Original-Commit: ac64ae92ff624f1befe3b973e0f0fd0204f2eac1
7 files changed
tree: a0650a4247dac43614ab513b767843323a3af1e1
  1. base/
  2. build/
  3. components/
  4. dbus/
  5. device/
  6. ipc/
  7. mojo/
  8. testing/
  9. third_party/
  10. ui/