Fix crash in InvokeOnMemoryDump when tracing

Fix crash in InvokeOnMemoryDump when tracing

Fixes a bug in ProcessMetricsMemoryDumpProvider::RegisterForProcess
where if we get a duplicate pid we register an MDP but then immediately
destroy it. This later causes a crash. Instead we should not register
the MDP if we get a duplicate pid. This won't help the root problem
of why we are getting duplicate pids which will now just cause
information loss instead of crashing.

BUG=695731
Review-Url: https://codereview.chromium.org/2753723003
Cr-Commit-Position: refs/heads/master@{#457392}
(cherry picked from commit 96f0a2b238852a56c0a30aa67f4a6943c5271688)

Review-Url: https://codereview.chromium.org/2761443003 .
Cr-Commit-Position: refs/branch-heads/3029@{#259}
Cr-Branched-From: 939b32ee5ba05c396eef3fd992822fcca9a2e262-refs/heads/master@{#454471}
Committed: https://chromium.googlesource.com/chromium/src/+/7bbe40435f169a7d163e703f42c0086f4133e005

[hjd, 2017-03-17 12:16:09]

Description was changed from

==========
Fix crash in InvokeOnMemoryDump when tracing

Fixes a bug in ProcessMetricsMemoryDumpProvider::RegisterForProcess
where if we get a duplicate pid we register an MDP but then immediately
destroy it. This later causes a crash. Instead we should not register
the MDP if we get a duplicate pid. This won't help the root problem
of why we are getting duplicate pids which will now just cause
information loss instead of crashing.

BUG=695731

Review-Url: https://codereview.chromium.org/2753723003
Cr-Commit-Position: refs/heads/master@{#457392}
(cherry picked from commit 96f0a2b238852a56c0a30aa67f4a6943c5271688)
==========

to

==========
Fix crash in InvokeOnMemoryDump when tracing

Fixes a bug in ProcessMetricsMemoryDumpProvider::RegisterForProcess
where if we get a duplicate pid we register an MDP but then immediately
destroy it. This later causes a crash. Instead we should not register
the MDP if we get a duplicate pid. This won't help the root problem
of why we are getting duplicate pids which will now just cause
information loss instead of crashing.

BUG=695731

Review-Url: https://codereview.chromium.org/2753723003
Cr-Commit-Position: refs/heads/master@{#457392}
(cherry picked from commit 96f0a2b238852a56c0a30aa67f4a6943c5271688)

Review-Url: https://codereview.chromium.org/2761443003 .
Cr-Commit-Position: refs/branch-heads/3029@{#259}
Cr-Branched-From:
939b32ee5ba05c396eef3fd992822fcca9a2e262-refs/heads/master@{#454471}
Committed:
https://chromium.googlesource.com/chromium/src/+/7bbe40435f169a7d163e703f42c0...
==========

[hjd, 2017-03-17 12:16:10]

Committed patchset #1 (id:1) manually as
7bbe40435f169a7d163e703f42c0086f4133e005.