Reviewers: ihab.awad, Description: ParserContext is a parse tree node builder which accumulates inputs and builds a parse tree node with the information it has.
This change just introduces the builder and some tests. A separate CL will replace the many variations of creating PTNs with this api. Please review this at http://codereview.appspot.com/2470041/ Affected files: A src/com/google/caja/parser/ParserContext.java A tests/com/google/caja/parser/ParserContextTest.java
