Don't delete persistent histogram file on normal exit.
Don't delete persistent histogram file on normal exit.

BUG=crashpad:165, chromium:696721

Change-Id: I85c6740955fdbdfd7f17208c095a4685e28bfacc
Reviewed-on: https://chromium-review.googlesource.com/448960
Commit-Queue: Sigurður Ásgeirsson <592632e08e8950241f83f5341243136380567d51@chromium.org>
Reviewed-by: Mark Mentovai <f1b5a91d4d6ad523f2610114591c007e75d15084@chromium.org>
Reviewed-by: Scott Graham <e134406e1863f3b48b0795831afac5c0595efb36@chromium.org>

atom/crashpad,chromium/crashpad,atom/crashpad,chromium/crashpad,chromium/crashpad,atom/crashpad