CSS aggregation strips some essential whitespace within strings

from @ridgerunner in #460448-28: Some CSS rules are broken once CSS aggregation is enabled

Your regex violates whitespace within strings. e.g. it destroys the following valid rule taken from the CSS spec: 4.1.7 Rule sets, declaration blocks, and selectors:

  p[example="public class foo\
  {\
      private int x;\
  \
      foo(int x) {\
          this.x = x;\
      }\
  \
  }"] { color: red }

A correct solution will never, ever, ever, change anything within any CSS string.

The only other area I can think of that may be a concern is within content: properties, but with whitespace collapsing in HTML is this an issue?