Unreviewed, rolling in r143348.

Unreviewed, rolling in r143348.
http://trac.webkit.org/changeset/143348
https://bugs.webkit.org/show_bug.cgi?id=110242

The bug was that isEmptyValue() was returning true for the deleted value.
Fixed this and simplified things further by delegating to m_sourceCode
for both isNull() and isHashTableDeletedValue(), so they can't be out of
sync.

* runtime/CodeCache.cpp:
(JSC::CodeCache::getFunctionExecutableFromGlobalCode):
* runtime/CodeCache.h:
(JSC::SourceCodeKey::SourceCodeKey):
(JSC::SourceCodeKey::isHashTableDeletedValue):
(JSC::SourceCodeKey::hash):
(JSC::SourceCodeKey::length):
(JSC::SourceCodeKey::isNull):
(JSC::SourceCodeKey::operator==):
(SourceCodeKey):

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@143384 268f45cc-cd09-0410-ab3c-d52691b4dbfc