validating that the hot path does not spill - somewhat simpler code.

Cleared the scenario where a range is defined in a deferred block. The
code before was slightly more complicated by not leveraging the
property that these sort of ranges would be completely contained within
deferred blocks.

Moved "spills in deferred blocks" marking to a more appropriate
location.

One thing this CL achieves is correct support for scenarios where a
range is spilled both on the deferred and then hot path, and the ranges
concatenate. I owe better unit testing, which I will add in a subsequent
CL.

BUG=

Review URL: https://codereview.chromium.org/1472803004

Cr-Commit-Position: refs/heads/master@{#32302}