[UMA] Rearrange some code in preparation for uploading additional profiler data.
This CL *should* be a pure code movement CL, with no functional changes,
except that it also causes drive metrics to be collected *prior* to fetching
profiler data, rather than after. This makes it easier to begin uploading
profiler data that spans more of Chrome's running time than just startup
(which will be implemented in a follow-up CL).
BUG=523207
TEST=none
R=asvitkine@chromium.org
Review URL: https://codereview.chromium.org/
1308723002
Cr-Commit-Position: refs/heads/master@{#345503}