GTTF: Remove possible interference between BlobURLRequestJob tests.
GTTF: Remove possible interference between BlobURLRequestJob tests.

Quite a lot of state was shared between tests, like a temporary directory,
some paths, and a Thread (which could possibly have some tasks still running).

This is risky, and we had problems with those in the past. ui_tests used to
reuse the same temporary directory, which caused problems with file collisions
and failure to delete files.

We had problems with net_unittests having posted tasks after the test that
started them has finished. It is very hard to debug and reproduce when it happens.

This change increases the test run time by 3 ms (5 ms before vs 8 ms after).
Arguably, the time savings are not worth a possible reliability problem.

BUG=none
TEST=test_shell_tests

Review URL: http://codereview.chromium.org/3281007

git-svn-id: http://src.chromium.org/svn/trunk/src@58085 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: 1bdfadc97917845ee4314d85a2b7eb2e7e39cb7b
meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser