Tweak RawVec::reserve{,_exact}.

[nnethercote]

r? @ghost

[nnethercote]

@bors try @rust-timer queue

[rust-timer]

Awaiting bors try build completion

[bors]

⌛ Trying commit 6fd1a56 with merge 8bb4a7a688108af7cea8b3a844f9b02fa1aca0df...

[bors]

☀️ Try build successful - checks-actions, checks-azure
Build commit: 8bb4a7a688108af7cea8b3a844f9b02fa1aca0df (8bb4a7a688108af7cea8b3a844f9b02fa1aca0df)

[rust-timer]

Queued 8bb4a7a688108af7cea8b3a844f9b02fa1aca0df with parent 1d601d6, future comparison URL.

[rust-timer]

Finished benchmarking try commit (8bb4a7a688108af7cea8b3a844f9b02fa1aca0df): comparison url.

Benchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. Please note that if the perf results are neutral, you should likely undo the rollup=never given below by specifying rollup- to bors.

Importantly, though, if the results of this run are non-neutral do not roll this PR up -- it will mask other regressions or improvements in the roll up.

@bors rollup=never

[mati865]

Slightly positive task-clock and wall-time.

[nnethercote]

Eh, it's a wash.