sync: Improve ModelAssociation event tracing

sync: Improve ModelAssociation event tracing

Take advantage of the ASYNC variants of the event tracing macros when
tracing model association times.  This makes the model association
tracing much more reliable and easier to read.

BUG=286541
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=221879

[rlarocque, 2013-09-06 23:51:56]

This should make tracing password association times easier.  :)

Please review.

[Raghu Simha, 2013-09-07 00:20:18]

This should definitely make tracing model association easier. I have one comment
below.

https://codereview.chromium.org/23907005/diff/1/chrome/browser/sync/glue/mode...
File chrome/browser/sync/glue/model_association_manager.cc (right):

https://codereview.chromium.org/23907005/diff/1/chrome/browser/sync/glue/mode...
chrome/browser/sync/glue/model_association_manager.cc:529:
currently_associating_);
I think the order of arguments in these calls is incorrect.

When TRACE_EVENT_BEGIN1 was being called, "DataType" corresponded to the
"arg1_name" parameter, and the model type string to "arg1_val".

In the new version where TRACE_EVENT_ASYNC_BEGIN1 is being called, "DataType"
now corresponds to the "id" parameter, the model type string to "arg1_name", and
the DTC pointer to "arg1_value".

I think |currently_associating_| ought to be the third argument in all three
calls.

[rlarocque, 2013-09-07 01:03:46]

The buggy argument ordering actually worked surprisingly well, but the correct
ordering works better.

Patch updated.  PTAL.

[Raghu Simha, 2013-09-07 01:27:53]

LGTM. Thanks for working on this!

On 2013/09/07 01:03:46, rlarocque wrote:
> The buggy argument ordering actually worked surprisingly well, but the correct
> ordering works better.

That's interesting. I suppose model association for different data types is done
serially? From the documentation in trace_event.h, |id| is used to match
different ASYNC_BEGIN events with their corresponding ASYNC_END events. When the
value of |id| was the string literal "DataType" (patch set 1), the tracing
events from model association events for different types should have gotten
mixed up in theory. Anyhow, glad it works now.

> 
> Patch updated.  PTAL.

[commit-bot: I haz the power, 2013-09-07 01:33:46]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/rlarocque@chromium.org/23907005/5001

[commit-bot: I haz the power, 2013-09-07 04:08:07]

Change committed as 221879