Don't leak ScopeChainNode's

Create a sub-scope of the global scope chain, rather than a completely new scope
chain.  Leaks are difficult to autotest, but an autotest for
QScriptDeclarativeClass::pushCleanContext() was added to ensure its behavior doesn't
regress.  To reproduce the leak (prior to this change) use:

while (true) {
    QScriptDeclarativeClass::pushCleanContext(&engine);
    engine.popContext();
}

Change-Id: I41ac61ea1664da569eb329c8276f2a0bb6d2f1f7
Task-number: QTBUG-17166
Reviewed-by: Martin Jones
(cherry picked from commit 3bc6f8d8dd630cd0298e27fc4b7430d2bf73a232)

Conflicts:

	tests/auto/declarative/qdeclarativeecmascript/tst_qdeclarativeecmascript.cpp

1 files changed, 1 insertions, 3 deletions

diff --git a/src/script/api/qscriptengine.cpp b/src/script/api/qscriptengine.cpp
index 478fdaa..d3e5f2f 100644
--- a/src/script/api/qscriptengine.cpp
+++ b/src/script/api/qscriptengine.cpp
@@ -2762,9 +2762,7 @@ JSC::CallFrame *QScriptEnginePrivate::pushContext(JSC::CallFrame *exec, JSC::JSV
         if (!clearScopeChain) {
             newCallFrame->init(0, /*vPC=*/0, exec->scopeChain(), exec, flags | ShouldRestoreCallFrame, argc, callee);
         } else {
-            JSC::JSObject *jscObject = originalGlobalObject();
-            JSC::ScopeChainNode *scn = new JSC::ScopeChainNode(0, jscObject, &exec->globalData(), exec->lexicalGlobalObject(), jscObject);
-            newCallFrame->init(0, /*vPC=*/0, scn, exec, flags | ShouldRestoreCallFrame, argc, callee);
+            newCallFrame->init(0, /*vPC=*/0, globalExec()->scopeChain(), exec, flags | ShouldRestoreCallFrame, argc, callee);
         }
     } else {
         setContextFlags(newCallFrame, flags);