Reviewed by Gavin Barraclough.

        JSONP is unnecessarily slow
        https://bugs.webkit.org/show_bug.cgi?id=62920

        JSONP has unfortunately become a fairly common idiom online, yet
        it triggers very poor performance in JSC as we end up doing codegen
        for a large number of property accesses that will
           * only be run once, so the vast amount of logic we dump to handle
             caching of accesses is unnecessary.
           * We are doing codegen that is directly proportional to just
             creating the object in the first place.

        This patch extends the use of the literal parser to JSONP-like structures
        in global code, handling a number of different forms I have seen online.
        In an extreme case this improves performance of JSONP by more than 2x
        due to removal of code generation and execution time, and a few optimisations
        that I made to the parser itself.

        * API/JSValueRef.cpp:
        (JSValueMakeFromJSONString):
        * interpreter/Interpreter.cpp:
        (JSC::Interpreter::callEval):
        (JSC::Interpreter::execute):
        * parser/Lexer.cpp:
        (JSC::Lexer::isKeyword):
        * parser/Lexer.h:
        * runtime/JSGlobalObjectFunctions.cpp:
        (JSC::globalFuncEval):
        * runtime/JSONObject.cpp:
        (JSC::JSONProtoFuncParse):
        * runtime/LiteralParser.cpp:
        (JSC::LiteralParser::tryJSONPParse):
        (JSC::LiteralParser::makeIdentifier):
        (JSC::LiteralParser::Lexer::lex):
        (JSC::LiteralParser::Lexer::next):
        (JSC::isSafeStringCharacter):
        (JSC::LiteralParser::Lexer::lexString):
        (JSC::LiteralParser::Lexer::lexNumber):
        (JSC::LiteralParser::parse):
        * runtime/LiteralParser.h:
        (JSC::LiteralParser::LiteralParser):
        (JSC::LiteralParser::tryLiteralParse):
        (JSC::LiteralParser::Lexer::Lexer):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@89184 268f45cc-cd09-0410-ab3c-d52691b4dbfc