Make sure DCHECK compiles out completely if DCHECKS aren't enabled.

Make sure DCHECK compiles out completely if DCHECKS aren't enabled.

The MSVC optimizer can get confused when expressions that create
temporaries are completely optimized out.

Before:
2017-01-24  05:59 PM         1,139,712 chrome.exe
2017-01-24  05:53 PM        48,618,496 chrome.dll
2017-01-24  05:59 PM        68,739,584 chrome_child.dll

After:
2017-01-24  06:51 PM         1,136,128 chrome.exe
2017-01-24  06:45 PM        48,265,216 chrome.dll
2017-01-24  06:51 PM        68,245,504 chrome_child.dll

This results in a total savings of ~830KB in a mostly official build.
These numbers don't include the effect of full_wpo_on_official=true,
but it's been confirmed that this codegen bug happens either way.

BUG=684105
R=scottmg@chromium.org

Review-Url: https://codereview.chromium.org/2653073002
Cr-Commit-Position: refs/heads/master@{#446054}
(cherry picked from commit fc670f47ae174fb59497fe5d3315b10cc7601cad)

Review-Url: https://codereview.chromium.org/2724253004 .
Cr-Commit-Position: refs/branch-heads/2987@{#741}
Cr-Branched-From: ad51088c0e8776e8dcd963dbe752c4035ba6dab6-refs/heads/master@{#444943}
Committed: https://chromium.googlesource.com/chromium/src/+/b6026eb7489ef89100fd8126b2a5d80d08bb9f45

[dcheng, 2017-03-02 19:49:40]

Description was changed from

==========
Make sure DCHECK compiles out completely if DCHECKS aren't enabled.

The MSVC optimizer can get confused when expressions that create
temporaries are completely optimized out.

Before:
2017-01-24  05:59 PM         1,139,712 chrome.exe
2017-01-24  05:53 PM        48,618,496 chrome.dll
2017-01-24  05:59 PM        68,739,584 chrome_child.dll

After:
2017-01-24  06:51 PM         1,136,128 chrome.exe
2017-01-24  06:45 PM        48,265,216 chrome.dll
2017-01-24  06:51 PM        68,245,504 chrome_child.dll

This results in a total savings of ~830KB in a mostly official build.
These numbers don't include the effect of full_wpo_on_official=true,
but it's been confirmed that this codegen bug happens either way.

BUG=684105
R=scottmg@chromium.org

Review-Url: https://codereview.chromium.org/2653073002
Cr-Commit-Position: refs/heads/master@{#446054}
(cherry picked from commit fc670f47ae174fb59497fe5d3315b10cc7601cad)
==========

to

==========
Make sure DCHECK compiles out completely if DCHECKS aren't enabled.

The MSVC optimizer can get confused when expressions that create
temporaries are completely optimized out.

Before:
2017-01-24  05:59 PM         1,139,712 chrome.exe
2017-01-24  05:53 PM        48,618,496 chrome.dll
2017-01-24  05:59 PM        68,739,584 chrome_child.dll

After:
2017-01-24  06:51 PM         1,136,128 chrome.exe
2017-01-24  06:45 PM        48,265,216 chrome.dll
2017-01-24  06:51 PM        68,245,504 chrome_child.dll

This results in a total savings of ~830KB in a mostly official build.
These numbers don't include the effect of full_wpo_on_official=true,
but it's been confirmed that this codegen bug happens either way.

BUG=684105
R=scottmg@chromium.org

Review-Url: https://codereview.chromium.org/2653073002
Cr-Commit-Position: refs/heads/master@{#446054}
(cherry picked from commit fc670f47ae174fb59497fe5d3315b10cc7601cad)

Review-Url: https://codereview.chromium.org/2724253004 .
Cr-Commit-Position: refs/branch-heads/2987@{#741}
Cr-Branched-From:
ad51088c0e8776e8dcd963dbe752c4035ba6dab6-refs/heads/master@{#444943}
Committed:
https://chromium.googlesource.com/chromium/src/+/b6026eb7489ef89100fd8126b2a5...
==========

[dcheng, 2017-03-02 19:49:41]

Committed patchset #1 (id:1) manually as
b6026eb7489ef89100fd8126b2a5d80d08bb9f45.