Chrome Version: trunk
OS: At least Windows

What steps will reproduce the problem?
(1) Try to use testRunner.setBackingScaleFactor and immediately end the test
(2) Note that the pixel result does not reflect the backing scale

What is the expected result?
testRunner.setBackingScaleFactor works without forcing a repaint

What happens instead?
Convoluted code is required to force a repaint. See LayoutTests/editing/caret/caret-painting-low-dpi.html

Other tests use setTimeout(0) and others seem to get it wrong entirely.

We need an easy to define and standard way to get this right.