Move the thread hop for UMA user actions from content:: to base::.

components/metrics/metrics_service.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 //------------------------------------------------------------------------------
 // Description of the life cycle of a instance of MetricsService.
 //
 //  OVERVIEW
 //
 // A MetricsService instance is typically created at application startup.  It is
@@ skipping 283 matching lines @@
       log_upload_in_progress_(false),
       idle_since_last_transmission_(false),
       session_id_(-1),
       self_ptr_factory_(this),
       state_saver_factory_(this) {
   DCHECK(IsSingleThreaded());
   DCHECK(state_manager_);
   DCHECK(client_);
   DCHECK(local_state_);
 
+  base::SetRecordActionTaskRunner(client_->GetUIThreadTaskRunner());

[Ilya Sherman, 2016/04/06 02:36:29]

I think it makes sense to set this in the same place where the action callback
is set.  But I'm curious, why did you choose to implement this here rather than
in that spot?

[beaudoin, 2016/04/06 15:06:13]

It seems that a RecordAction is being called before
MetricsService::EnableRecording has been called. If I don't do this here I get a
DCHECK triggered by:

https://code.google.com/p/chromium/codesearch#chromium/src/chrome/browser/the...

I imagine it worked before because thread_checker picked up the thread at that
point, even though the action is never recorded since the Callbacks are not set
yet.

We should probably figure out why that RecordAction is happening too early
though.

[Ilya Sherman, 2016/04/06 21:48:48]

Hmm, yeah, that sounds like a bug for sure -- there's not much point in
recording a metric if it's just silently dropped.  Could you please file a bug
for this?  I think it would be nice to track that down and fix it before landing
this code, since this code is currently more complicated to work around that
bug.

[beaudoin, 2016/04/07 18:12:34]

Filed as: https://crbug.com/601482

I'll take a look. Not sure I'll be able to do much better than remove the Record
call, I wouldn't be comfortable fiddling with the startup sequence.

+
   // Set the install date if this is our first run.
   int64_t install_date = local_state_->GetInt64(prefs::kInstallDate);
   if (install_date == 0)
     local_state_->SetInt64(prefs::kInstallDate, base::Time::Now().ToTimeT());
 }
 
 MetricsService::~MetricsService() {
   DisableRecording();
 }
 
@@ skipping 847 matching lines @@
                  base::Time::Now().ToTimeT());
 }
 
 void MetricsService::SkipAndDiscardUpload() {
   log_manager_.DiscardStagedLog();
   scheduler_->UploadCancelled();
   log_upload_in_progress_ = false;
 }
 
 }  // namespace metrics