This API was replaced with base::AssertBlockingAllowed().

This CL is a search-and-replace:
s/ThreadRestrictions::AssertIOAllowed()/AssertBlockingAllowed()/
and some manual changes in thread_restrictions.h.

TBR=jam@chromium.org

Bug: 766678
Cq-Include-Trybots: master.tryserver.chromium.android:android_optional_gpu_tests_rel;master.tryserver.chromium.linux:linux_optional_gpu_tests_rel;master.tryserver.chromium.mac:ios-simulator-cronet;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel;master.tryserver.chromium.win:win10_chromium_x64_rel_ng;master.tryserver.chromium.win:win_optional_gpu_tests_rel
Change-Id: I05700504c1556da5dee39c1206df5ddd676a2cee
Reviewed-on: https://chromium-review.googlesource.com/728364


Commit-Queue: François Doray <fdoray@chromium.org>
Reviewed-by: Gabriel Charette <gab@chromium.org>
Reviewed-by: Robert Liao <robliao@chromium.org>
Cr-Commit-Position: refs/heads/master@{#510422}