Small changes in preparation for Hydrogen-generated KeyedLoadGeneric

R=mvstanton@chromium.org

Review URL: https://codereview.chromium.org/303583002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@21535 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Reland 21529 - "Add a flag to d8 to invoke weak callbacks"

> This will send an idle notification and a low memory notification after
> each test.
>
> For some reason it's not enough to send a low memory notification alone.
>
> BUG=none
> R=yangguo@chromium.org
> LOG=n

BUG=none
R=yangguo@chromium.org
LOG=n

Review URL: https://codereview.chromium.org/297213006

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@21536 ce2b1a6d-e550-0410-aec6-3dcde31c8c00