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

Review URL: https://codereview.chromium.org/1211883003

Cr-Commit-Position: refs/heads/master@{#336232}

1 files changed, 2 insertions, 3 deletions

diff --git a/components/tracing/tracing_messages.h b/components/tracing/tracing_messages.h
index dd14b90..ebdefc1 100644
--- a/components/tracing/tracing_messages.h
+++ b/components/tracing/tracing_messages.h
@@ -32,10 +32,9 @@ IPC_ENUM_TRAITS_MAX_VALUE(
     static_cast<int>(base::trace_event::MemoryDumpType::LAST))
 
 // Sent to all child processes to enable trace event recording.
-IPC_MESSAGE_CONTROL3(TracingMsg_BeginTracing,
+IPC_MESSAGE_CONTROL2(TracingMsg_BeginTracing,
                      std::string /*  trace_config_str */,
-                     base::TraceTicks /* browser_time */,
-                     int /* Tracing process id (hash of child id) */)
+                     base::TraceTicks /* browser_time */)
 
 // Sent to all child processes to disable trace event recording.
 IPC_MESSAGE_CONTROL0(TracingMsg_EndTracing)