* Several changes targeted to improving perf of RazorSyntaxTree.Parse
1) Modify ParserHelpers.IsNewLine to use a switch instead of Array.IndexOf
2) Modify Tokenizer.CreateToken to take in an array of RazorDiagnostics rather than an IReadOnlyList as that was causing a ToArray call on an empty diagnostics very often (during a SyntaxFactory.Token call)
3) Modify TokenizerBackedParser.Putback to allow an IReadOnlyList as a parameter to not require creation of a reverse enumerator.
4) Cut down allocations in HtmlMarkupParser.GetParserState by:
a) Using an IReadOnlyList instead of IEnumerable to get rid of the allocations from the .any calls
b) Don't allocate while reading initial spacing
c) Inline the IsSpacingToken code so cut down on code executed and need to allocate a separate Func
5) Modify CSharpCodeParser.IsSpacingToken to now be a set of methods instead of a single method that allocates a Func. This is a very high traffic method.
6) Implement a fairly rudimentary Whitespace token cache, as they can be reused. This was based off Roslyn's SyntaxNodeCache, but simplified significantly. It's probably worth investigating whether you should more fully embrance token caching outside of whitespace.
* PR feedback and added one more optimization in LocateOwner that's been bugging me for years. Assuming all chidlren are contained within a nodes span, we can short-circuit the DFS this code was doing significantly cutting time in this method which is important as it's exercised on the main thread during typing.
* missed a space
* StringTextToSnapshot's switch to IsNewLine needed to use start as the index to begin the search, not zero.\n\nCommit migrated from 45411f7526
b0d819f1e8