Speculative workaround for VS 2015 code-gen bug

Speculative workaround for VS 2015 code-gen bug

On PGO builds (but no others) a pair of functions in
process_power_collector.cc get compiled such that the callee returns a
floating-point value in xmm0 and the caller looks for it in st(0). The
details are in the bug, but if floating-point exceptions are enabled
(perhaps happening due to third-party injected software changing the FPU
state) then this can lead to crashes. Even without the crashes it is
clearly wrong.

Since the bug only reproes in PGO it is difficult to test a fix but
disabling optimizations around the two functions *should* do the trick.

BUG=640588
Review-Url: https://codereview.chromium.org/2329693002
Cr-Commit-Position: refs/heads/master@{#417994}
(cherry picked from commit 764c7362bc01b0f1765f2f9043ca89b71a8d0c76)

Committed: https://chromium.googlesource.com/chromium/src/+/5c246eb9899a1d95594254b0db36a47e8f9763ae

[brucedawson, 2016-09-14 21:10:18]

Description was changed from

==========
Speculative workaround for VS 2015 code-gen bug

On PGO builds (but no others) a pair of functions in
process_power_collector.cc get compiled such that the callee returns a
floating-point value in xmm0 and the caller looks for it in st(0). The
details are in the bug, but if floating-point exceptions are enabled
(perhaps happening due to third-party injected software changing the FPU
state) then this can lead to crashes. Even without the crashes it is
clearly wrong.

Since the bug only reproes in PGO it is difficult to test a fix but
disabling optimizations around the two functions *should* do the trick.

BUG=640588

Review-Url: https://codereview.chromium.org/2329693002
Cr-Commit-Position: refs/heads/master@{#417994}
(cherry picked from commit 764c7362bc01b0f1765f2f9043ca89b71a8d0c76)
==========

to

==========
Speculative workaround for VS 2015 code-gen bug

On PGO builds (but no others) a pair of functions in
process_power_collector.cc get compiled such that the callee returns a
floating-point value in xmm0 and the caller looks for it in st(0). The
details are in the bug, but if floating-point exceptions are enabled
(perhaps happening due to third-party injected software changing the FPU
state) then this can lead to crashes. Even without the crashes it is
clearly wrong.

Since the bug only reproes in PGO it is difficult to test a fix but
disabling optimizations around the two functions *should* do the trick.

BUG=640588

Review-Url: https://codereview.chromium.org/2329693002
Cr-Commit-Position: refs/heads/master@{#417994}
(cherry picked from commit 764c7362bc01b0f1765f2f9043ca89b71a8d0c76)

Committed:
https://chromium.googlesource.com/chromium/src/+/5c246eb9899a1d95594254b0db36...
==========

[brucedawson, 2016-09-14 21:10:19]

Committed patchset #1 (id:1) manually as
5c246eb9899a1d95594254b0db36a47e8f9763ae.