The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/7947ccd5754451960f0bf18f3b5401dc5ffeedb8

commit 7947ccd5754451960f0bf18f3b5401dc5ffeedb8
Author: lukasza <lukasza@chromium.org>
Date: Thu Jul 28 21:56:25 2016

More aggressive IO asserts in content_browsertests.

Since browser test's main thread corresponds roughly to the product's UI
thread, it should behave in the same wrt base::ThreadRestrictions -
after this CL the body of browser tests derived from
content::ContentBrowserTest is not allowed to do file IO.

Motivation: The more aggressive IO asserts would have caught
 https://crbug.com/626972  earlier.  Hopefully the more aggressive
asserting will also prevent future regressions in this area.

BUG= 631145 

Review-Url: https://codereview.chromium.org/2175933002
Cr-Commit-Position: refs/heads/master@{#408496}

[modify] https://crrev.com/7947ccd5754451960f0bf18f3b5401dc5ffeedb8/PRESUBMIT.py
[modify] https://crrev.com/7947ccd5754451960f0bf18f3b5401dc5ffeedb8/content/browser/accessibility/dump_accessibility_browsertest_base.cc
[modify] https://crrev.com/7947ccd5754451960f0bf18f3b5401dc5ffeedb8/content/browser/accessibility/dump_accessibility_events_browsertest.cc
[modify] https://crrev.com/7947ccd5754451960f0bf18f3b5401dc5ffeedb8/content/browser/accessibility/dump_accessibility_tree_browsertest.cc
[modify] https://crrev.com/7947ccd5754451960f0bf18f3b5401dc5ffeedb8/content/browser/cross_site_transfer_browsertest.cc
[modify] https://crrev.com/7947ccd5754451960f0bf18f3b5401dc5ffeedb8/content/browser/download/download_browsertest.cc
[modify] https://crrev.com/7947ccd5754451960f0bf18f3b5401dc5ffeedb8/content/browser/download/mhtml_generation_browsertest.cc
[modify] https://crrev.com/7947ccd5754451960f0bf18f3b5401dc5ffeedb8/content/browser/indexed_db/indexed_db_browsertest.cc
[modify] https://crrev.com/7947ccd5754451960f0bf18f3b5401dc5ffeedb8/content/browser/media/webrtc/webrtc_audio_debug_recordings_browsertest.cc
[modify] https://crrev.com/7947ccd5754451960f0bf18f3b5401dc5ffeedb8/content/browser/media/webrtc/webrtc_getusermedia_browsertest.cc
[modify] https://crrev.com/7947ccd5754451960f0bf18f3b5401dc5ffeedb8/content/browser/renderer_host/render_view_host_browsertest.cc
[modify] https://crrev.com/7947ccd5754451960f0bf18f3b5401dc5ffeedb8/content/browser/tracing/tracing_controller_browsertest.cc
[modify] https://crrev.com/7947ccd5754451960f0bf18f3b5401dc5ffeedb8/content/browser/webui/web_ui_mojo_browsertest.cc
[modify] https://crrev.com/7947ccd5754451960f0bf18f3b5401dc5ffeedb8/content/public/test/content_browser_test.cc
[modify] https://crrev.com/7947ccd5754451960f0bf18f3b5401dc5ffeedb8/content/public/test/content_browser_test_utils.cc
[modify] https://crrev.com/7947ccd5754451960f0bf18f3b5401dc5ffeedb8/content/public/test/content_browser_test_utils.h
[modify] https://crrev.com/7947ccd5754451960f0bf18f3b5401dc5ffeedb8/content/renderer/dom_serializer_browsertest.cc
[modify] https://crrev.com/7947ccd5754451960f0bf18f3b5401dc5ffeedb8/content/test/content_browser_test_test.cc
[modify] https://crrev.com/7947ccd5754451960f0bf18f3b5401dc5ffeedb8/content/test/ppapi/ppapi_test.cc
[modify] https://crrev.com/7947ccd5754451960f0bf18f3b5401dc5ffeedb8/content/test/webui_resource_browsertest.cc
[modify] https://crrev.com/7947ccd5754451960f0bf18f3b5401dc5ffeedb8/net/cert/test_root_certs.cc
[modify] https://crrev.com/7947ccd5754451960f0bf18f3b5401dc5ffeedb8/net/test/embedded_test_server/embedded_test_server.cc
[modify] https://crrev.com/7947ccd5754451960f0bf18f3b5401dc5ffeedb8/net/test/spawned_test_server/local_test_server.cc
[modify] https://crrev.com/7947ccd5754451960f0bf18f3b5401dc5ffeedb8/net/test/test_data_directory.cc