Fix serialization of expected outcomes in test driver.

The outcomes are saved as a set and need to be converted into
a list to be json-serializable.

TBR=tandrii@chromium.org

Review URL: https://codereview.chromium.org/710073002

Cr-Commit-Position: refs/heads/master@{#25246}
git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@25246 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Fix bugs in simplified lowering relating to int32/uint32 signs.

Lowering of NumberToUint32 and NumberToInt32 was not correctly accounting for the sign of the input and the sign of the output, emitting the wrong representation changes.

Along the way, I've found cases where MachineOperatorBuilder would break if fed a machine type for loads or stores that was not cached, requiring MachineOperatorBuilder to take zone to allocate operators for these cases.

R=bmeurer@chromium.org, jarin@chromium.org
BUG=

Review URL: https://codereview.chromium.org/714613002

Cr-Commit-Position: refs/heads/master@{#25247}
git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@25247 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Fix has_constant_parameter_count() confusion in LReturn

BUG=chromium:431602
LOG=y
R=jarin@chromium.org

Review URL: https://codereview.chromium.org/714663002

Cr-Commit-Position: refs/heads/master@{#25249}
git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@25249 ce2b1a6d-e550-0410-aec6-3dcde31c8c00