Use testharness.js instead of js-test.js in LayoutTests/fast/canvas tests.

This change replaces js-test.js assertions with testharness.js assertions. The expectation files are removed as they are not needed anymore.
To simplify review and landing, each change corrects 10 tests.

BUG=639732

Review-Url: https://codereview.chromium.org/2675763005
Cr-Commit-Position: refs/heads/master@{#449394}