A combination of bugs caused this function to almost always jump to runtime
which is why most tests passed.

BUG=
TEST=sputnik/S15.5.4.13_A2_T6

Review URL: https://chromiumcodereview.appspot.com/9382005
Patch from Daniel Kalmar <kalmard@homejinni.com>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@10678 ce2b1a6d-e550-0410-aec6-3dcde31c8c00