Implement ES6 class syntax without inheritance support

Implement ES6 class syntax without inheritance support
https://bugs.webkit.org/show_bug.cgi?id=140918

Reviewed by Geoffrey Garen.

Source/JavaScriptCore:

Added the most basic support for ES6 class syntax. After this patch, we support basic class definition like:
class A {
    constructor() { }
    someMethod() { }
}

We'll add the support for "extends" keyword and automatically generating a constructor in follow up patches.
We also don't support block scoping of a class declaration.

We support both class declaration and class expression. A class expression is implemented by the newly added
ClassExprNode AST node. A class declaration is implemented by ClassDeclNode, which is a thin wrapper around
AssignResolveNode.

Tests: js/class-syntax-declaration.html
       js/class-syntax-expression.html

* bytecompiler/NodesCodegen.cpp:
(JSC::ObjectLiteralNode::emitBytecode): Create a new object instead of delegating the work to PropertyListNode.
Also fixed the 5-space indentation.
(JSC::PropertyListNode::emitBytecode): Don't create a new object now that ObjectLiteralNode does this.
(JSC::ClassDeclNode::emitBytecode): Added. Just let the AssignResolveNode node emit the byte code.
(JSC::ClassExprNode::emitBytecode): Create the class constructor and add static methods to the constructor by
emitting the byte code for PropertyListNode. Add instance methods to the class's prototype object the same way.

* parser/ASTBuilder.h:
(JSC::ASTBuilder::createClassExpr): Added. Creates a ClassExprNode.
(JSC::ASTBuilder::createClassDeclStatement): Added. Creates a AssignResolveNode and wraps it by a ClassDeclNode.

* parser/NodeConstructors.h:
(JSC::ClassDeclNode::ClassDeclNode): Added.
(JSC::ClassExprNode::ClassExprNode): Added.

* parser/Nodes.h:
(JSC::ClassExprNode): Added.
(JSC::ClassDeclNode): Added.

* parser/Parser.cpp:
(JSC::Parser<LexerType>::parseStatement): Added the support for class declaration.
(JSC::stringForFunctionMode): Return "method" for MethodMode.
(JSC::Parser<LexerType>::parseClassDeclaration): Added. Uses parseClass to create a class expression and wraps
it with ClassDeclNode as described above.
(JSC::Parser<LexerType>::parseClass): Parses a class expression.
(JSC::Parser<LexerType>::parseProperty):
(JSC::Parser<LexerType>::parseGetterSetter): Extracted from parseProperty to share the code between parseProperty
and parseClass.
(JSC::Parser<LexerType>::parsePrimaryExpression): Added the support for class expression.

* parser/Parser.h:
(FunctionParseMode): Added MethodMode.

* parser/SyntaxChecker.h:
(JSC::SyntaxChecker::createClassExpr): Added.
(JSC::SyntaxChecker::createClassDeclStatement): Added.

LayoutTests:

Added two tests for class declarations and class expressions.

* TestExpectations:
* js/class-syntax-declaration-expected.txt: Added.
* js/class-syntax-declaration.html: Added.
* js/class-syntax-expression-expected.txt: Added.
* js/class-syntax-expression.html: Added.
* js/script-tests/class-syntax-declaration.js: Added.
* js/script-tests/class-syntax-expression.js: Added.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@179371 268f45cc-cd09-0410-ab3c-d52691b4dbfc