Remove @host @-rules.

@host @-rules was deprecated. We should remove the code from Blink.

BUG=321956

Review URL: https://codereview.chromium.org/77053006

git-svn-id: svn://svn.chromium.org/blink/trunk@162613 bbb929c8-8fbe-4397-9dbb-9b2b20218538
[websql] Remove support for unscheduling tasks

Instead, have tasks check that the database they're operating on still
is open.

This brings us closer to the WebThread API which does not allow for
unscheduling tasks.

BUG=301514
R=michaeln@chromium.org

Review URL: https://codereview.chromium.org/83383003

git-svn-id: svn://svn.chromium.org/blink/trunk@162615 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Check the result of DocumentThreadableLoader::create in mainThreadCreateLoader.

This CL is almost same as https://codereview.chromium.org/78393002 which is reverted in https://codereview.chromium.org/84883004/.
In this CL I reduced the file read request count in the test case to avoid another crash bug (http://crbug.com/295428).

BUG=

Review URL: https://codereview.chromium.org/84693006

git-svn-id: svn://svn.chromium.org/blink/trunk@162616 bbb929c8-8fbe-4397-9dbb-9b2b20218538