We have been calling testGridTemplateColumnsRows() with
and without arrays.
Arrays are needed because the serialization of 2 tracks of the same size
can be "100px 100px" or "repeat(2, 100px)".
But in the rest of the cases we don't need an array,
so we call the method with a single value.
testGridTemplateColumnsRows() was not ready to support that,
and it wasn't actually checking anything in that case.

The patch modifies testing-utils.js, so it wraps values in an array
when required.
Now testGridTemplateColumnsRows() will be actually checking things.

Change-Id: I7e360677c391df74dedb474922bf5c04247141c5
Reviewed-on: https://chromium-review.googlesource.com/973063
Reviewed-by: Sergio Villar <svillar@igalia.com>
Commit-Queue: Manuel Rego Casasnovas <rego@igalia.com>
Cr-Commit-Position: refs/heads/master@{#544681}