Do all sample processing eagerly

Instead of applying normalization and millisecond to second conversion
in the UI, apply it when parsing test results. This makes it easier to
handle micro tests, which do not have this concept.
Wrap the canvas-micro-test harness

Wrap the harness to use a WebKitGTK+ build directory.
Allow running canvas tests with CairoGL

When appropriate activate accelerated 2D canvas when running canvas
micro tests.
Take three samples for every canvas micro test run