Replace most callers of nextInputChar with peekWithoutReplacement in CSSTokenizer.

This saves us a branch at each call site since we don't need to check
for NUL characters.

BUG=605792

Review-Url: https://codereview.chromium.org/2167073002
Cr-Commit-Position: refs/heads/master@{#407044}
1 file changed