Tidy up ComputedStyle::applyTransform

Use range-based for-loops when iterating transform operations (also in
ComputedStyle::requireTransformOrigin), since it's both tidier and
avoids unnecessary index-checks (in operator[].)
Move computation of offsetX/offsetY closer to their point of usage.
Extract the size of the bounding box once, and also drop some unneeded
qualifications of enumeration values.

BUG=369942

Review-Url: https://codereview.chromium.org/2474043002
Cr-Commit-Position: refs/heads/master@{#429598}
1 file changed