Produce cached data only for scripts which compile without errors.

ScriptCompiler::CompileUnbound handles cached data only when there was no
compilation error, so, if we produce the data for erroneous scripts, the
ScriptData object is leaked.

In addition, producing cached data for erroneous scripts makes little sense.

R=ulan@chromium.org
BUG=370327
LOG=N

Review URL: https://codereview.chromium.org/266423003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@21164 ce2b1a6d-e550-0410-aec6-3dcde31c8c00