Leaks tool reports false memory leaks due to Rope implementation.

Reviewed by Oliver Hunt.

JavaScriptCore: 

A rope is a recursive data structure where each node in the rope holds a set of
pointers, each of which may reference either a string (in UStringImpl form) or
another rope node.  A low bit in each pointer is used to distinguish between
rope & string elements, in a fashion similar to the recently-removed
PtrAndFlags class (see https://bugs.webkit.org/show_bug.cgi?id=33731 ).  Again,
this causes a problem for Leaks – refactor to remove the magic pointer
mangling.

Move Rope out from JSString.h and rename to URopeImpl, to match UStringImpl.
Give UStringImpl and URopeImpl a common parent class, UStringOrRopeImpl.
Repurpose an otherwise invalid permutation to flags (static & should report
memory cost) to identify ropes.

This allows us to change the rope's fibers to interrogate the object rather
than storing a bool within the low bits of the pointer (or in some cases the
use of a common parent class removes the need to determine the type at all -
there is a common interface to ref or get the length of either ropes or strings).

* API/JSClassRef.cpp:
(OpaqueJSClass::OpaqueJSClass):
(OpaqueJSClassContextData::OpaqueJSClassContextData):
* bytecompiler/BytecodeGenerator.cpp:
(JSC::keyForCharacterSwitch):
* interpreter/Interpreter.cpp:
(JSC::Interpreter::privateExecute):
* jit/JITStubs.cpp:
(JSC::DEFINE_STUB_FUNCTION):
* runtime/ArrayPrototype.cpp:
(JSC::arrayProtoFuncToString):
* runtime/Identifier.cpp:
(JSC::Identifier::equal):
(JSC::Identifier::addSlowCase):
* runtime/JSString.cpp:
(JSC::JSString::resolveRope):
* runtime/JSString.h:
(JSC::):
(JSC::RopeBuilder::JSString):
(JSC::RopeBuilder::~JSString):
(JSC::RopeBuilder::appendStringInConstruct):
(JSC::RopeBuilder::appendValueInConstructAndIncrementLength):
(JSC::RopeBuilder::JSStringFinalizerStruct::JSStringFinalizerStruct):
(JSC::RopeBuilder::JSStringFinalizerStruct::):
* runtime/UString.cpp:
(JSC::UString::toStrictUInt32):
(JSC::equal):
* runtime/UString.h:
(JSC::UString::isEmpty):
(JSC::UString::size):
* runtime/UStringImpl.cpp:
(JSC::URopeImpl::derefFibersNonRecursive):
(JSC::URopeImpl::destructNonRecursive):
* runtime/UStringImpl.h:
(JSC::UStringOrRopeImpl::isRope):
(JSC::UStringOrRopeImpl::length):
(JSC::UStringOrRopeImpl::ref):
(JSC::UStringOrRopeImpl::):
(JSC::UStringOrRopeImpl::operator new):
(JSC::UStringOrRopeImpl::UStringOrRopeImpl):
(JSC::UStringImpl::adopt):
(JSC::UStringImpl::createUninitialized):
(JSC::UStringImpl::tryCreateUninitialized):
(JSC::UStringImpl::data):
(JSC::UStringImpl::cost):
(JSC::UStringImpl::deref):
(JSC::UStringImpl::UStringImpl):
(JSC::UStringImpl::):
(JSC::URopeImpl::tryCreateUninitialized):
(JSC::URopeImpl::initializeFiber):
(JSC::URopeImpl::fiberCount):
(JSC::URopeImpl::fibers):
(JSC::URopeImpl::deref):
(JSC::URopeImpl::URopeImpl):
(JSC::URopeImpl::hasOneRef):
(JSC::UStringOrRopeImpl::deref):

WebCore: 

Renamed cUStringImpl::size() to UStringImpl::size()UStringImpl::length()
(matches WebCore::StringImpl).

* bridge/jni/jsc/JavaStringJSC.h:
(JSC::Bindings::JavaStringImpl::length):
* platform/text/AtomicString.cpp:
(WebCore::AtomicString::add):
(WebCore::AtomicString::find):



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@54843 268f45cc-cd09-0410-ab3c-d52691b4dbfc