Update StyleValue.cssString() to use existing methods instead of rolling our own.
All StyleValues now use toCSSValue()->cssText() instead of defining
custom methods in subclasses.
Conveniently, this effectively allows toCSSValue to be tested in
LayoutTests. Also get rid of re-parsing unit types in
SimpleLength.toCSSValue, since the code there had a bug anyway
which was uncovered by the LayoutTests.
BUG=
545318
Committed:
https://crrev.com/13eeea65976892b0c083bee1f354715bc67e5375
Cr-Commit-Position: refs/heads/master@{#370341}