Unflake inspector/profiler/heap-snapshot-loader.html

Temp filesystem storage is now cleared before running the test.

BUG=330617
R=alph@chromium.org

Review URL: https://codereview.chromium.org/136103004

git-svn-id: svn://svn.chromium.org/blink/trunk@164956 bbb929c8-8fbe-4397-9dbb-9b2b20218538