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- Changed the path to the simulator shared resources directory, where
the app also write rights, and won't be deleted after app is killed.
- Added "%m" to the file name, so that on-line profile merging is
enabled.
- Added a generated UUID to the file name, so that there won't be a
conflict when multiple apps are launched in one test suite.

Please see ios code coverage design doc for rationales of those changes:
go/bling-code-coverage-doc.

Bug: 1043273
Change-Id: I21b2c8f4018036fdd13eecbe7e1362c926886eca
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2031673
Commit-Queue: Zhaoyang Li <zhaoyangli@chromium.org>
Reviewed-by: John Budorick <jbudorick@chromium.org>
Reviewed-by: Eugene But <eugenebut@chromium.org>
Reviewed-by: Yuke Liao <liaoyuke@chromium.org>
Cr-Commit-Position: refs/heads/master@{#738365}