POSIX: In functions where we wait for a process with timeout, increment the amount of time we sleep between polls from 1 to 256 milliseconds instead of always sleeping 250 milliseconds.
POSIX: In functions where we wait for a process with timeout, increment the amount of time we sleep between polls from 1 to 256 milliseconds instead of always sleeping 250 milliseconds.

BUG=none
TEST=Perf tests that use WaitForSingleProcess but finishes under 250 ms will get more accurate results.
Review URL: http://codereview.chromium.org/1518008

git-svn-id: dd90618784b6a4b323ea0c23a071cb1c9e6f2ac7@43463 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

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