Cherry-pick: Fix threading issue in StreamTextureProxyImpl

Cherry-pick of https://codereview.chromium.org/575293003/ PS2

BindToLoop need to set |loop_| synchronously to prevent delete from
destroying the object on the wrong thread.

BUG: 17354106
Change-Id: I3168bb9c27fa135e0c98eb018610218e65455f0a
2 files changed