Use Vector::reserveInitialCapacity() when possible in JavaScriptCore runtime
https://bugs.webkit.org/show_bug.cgi?id=114111

Reviewed by Andreas Kling.

Almost all the code was already using Vector::reserveInitialCapacity()
and Vector::uncheckedAppend(). Fix the remaining parts.

* runtime/ArgList.h:
(MarkedArgumentBuffer): The type VectorType is unused.

* runtime/ArrayPrototype.cpp:
(JSC::arrayProtoFuncSort):
Move the variable closer to where it is needed.

* runtime/JSArray.cpp:
(JSC::JSArray::setLengthWithArrayStorage):
* runtime/JSObject.cpp:
(JSC::JSObject::getOwnPropertyNames):


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@147887 268f45cc-cd09-0410-ab3c-d52691b4dbfc