Revert of [tracing] Send unique tracing process id for cross-process memory dumps identification.

Revert of [tracing] Send unique tracing process id for cross-process memory dumps identification. (patchset #15 id:320001 of https://codereview.chromium.org/1173263004/)

Reason for revert:
Appears to regress sizes

PERF_REGRESS: chrome-si/initializers (14.29%), chrome-si/initializers (14.29%)

https://build.chromium.org/p/chromium/builders/Linux%20x64/builds/5461

Original issue's description:
> [tracing] Send unique tracing process id for cross-process memory dumps identification.
>
> The memory shared between browser and renderer must be identified with
> the same unique id for memory dumps in tracing. Currently the child
> process is not aware of its unique child process id. But, the child
> process id cannot be exposed in the child process (see discussion in
> crrev.com/1155683009).
>
> So, a hash of the child process id allocated by the browser process is
> sent to child process along with begin tracing message and will be
> exposed in the child process MemoryDumpManager. The allocator that
> needs to create a global guid will use the id to identify memory dumps.
>
> See the design doc https://goo.gl/ncMfUV for more details.
>
> BUG=497726
>
> Committed: https://crrev.com/a3e7c30a16e711b59226da21f993522ee47ac674
> Cr-Commit-Position: refs/heads/master@{#336210}

TBR=dcheng@chromium.org,jam@chromium.org,picksi@google.com,primiano@chromium.org,ssid@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=497726
Committed: https://crrev.com/7bab3b2fe54de87069eea91bc21743955063b213
Cr-Commit-Position: refs/heads/master@{#336232}

[Mike Wittman, 2015-06-25 19:40:20]

Created Revert of [tracing] Send unique tracing process id for cross-process
memory dumps identification.

[commit-bot: I haz the power, 2015-06-25 19:41:05]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1211883003/1

[commit-bot: I haz the power, 2015-06-25 19:42:26]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-06-25 19:43:32]

Patchset 1 (id:??) landed as
https://crrev.com/7bab3b2fe54de87069eea91bc21743955063b213
Cr-Commit-Position: refs/heads/master@{#336232}