[Cronet iOS] Add base::StatisticsRecorder::IsActive() check

[Cronet iOS] Add base::StatisticsRecorder::IsActive() check

This CL adds a base::StatisticsRecorder::IsActive() check when user calls
GetHistogramDeltas().

BUG=707836
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.android:android_cronet_tester

[xunjieli, 2017-04-06 21:36:14]

Description was changed from

==========
[Cronet iOS] Add base::StatisticsRecorder::IsActive() check

This CL adds a base::StatisticsRecorder::IsActive() check when user calls
GetHistogramDeltas().

BUG=707836
==========

to

==========
[Cronet iOS] Add base::StatisticsRecorder::IsActive() check

This CL adds a base::StatisticsRecorder::IsActive() check when user calls
GetHistogramDeltas().

BUG=707836
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.android:android_cronet_tester
==========

[xunjieli, 2017-04-06 21:36:42]

xunjieli@chromium.org changed reviewers:
+ mef@chromium.org

[xunjieli, 2017-04-06 21:36:43]

Misha: PTAL.

[xunjieli, 2017-04-06 21:37:30]

https://codereview.chromium.org/2801603008/diff/1/components/cronet/ios/crone...
File components/cronet/ios/cronet_environment.mm (right):

https://codereview.chromium.org/2801603008/diff/1/components/cronet/ios/crone...
components/cronet/ios/cronet_environment.mm:128:
base::StatisticsRecorder::Initialize();
We are calling base::StatisticsRecorder::Initialize() here

[mef, 2017-04-06 22:08:11]

https://codereview.chromium.org/2801603008/diff/1/components/cronet/ios/crone...
File components/cronet/ios/cronet_environment.mm (right):

https://codereview.chromium.org/2801603008/diff/1/components/cronet/ios/crone...
components/cronet/ios/cronet_environment.mm:128:
base::StatisticsRecorder::Initialize();
On 2017/04/06 21:37:29, xunjieli wrote:
> We are calling base::StatisticsRecorder::Initialize() here

I wonder whether it should happen after message loop is created? WDYT?

https://codereview.chromium.org/2801603008/diff/1/components/cronet/ios/crone...
components/cronet/ios/cronet_environment.mm:352:
DCHECK(base::StatisticsRecorder::IsActive());
What would happen if they call this on background thread before init completes?

[xunjieli, 2017-04-06 23:58:01]

https://codereview.chromium.org/2801603008/diff/1/components/cronet/ios/crone...
File components/cronet/ios/cronet_environment.mm (right):

https://codereview.chromium.org/2801603008/diff/1/components/cronet/ios/crone...
components/cronet/ios/cronet_environment.mm:352:
DCHECK(base::StatisticsRecorder::IsActive());
On 2017/04/06 22:08:11, mef wrote:
> What would happen if they call this on background thread before init
completes?

Is there an entry point  (if not CronetEnvironment::Initialize()) which
guarantees to complete before GetHistogramDeltas() is called?
On Android, we are doing StatisticsRecorder::Initialize() in JNIOnload() which
guarantees to be called before the user could do
CronetEngine.GetHistogramDeltas().

[mef, 2017-04-07 20:49:33]

On 2017/04/06 23:58:01, xunjieli wrote:
>
https://codereview.chromium.org/2801603008/diff/1/components/cronet/ios/crone...
> File components/cronet/ios/cronet_environment.mm (right):
> 
>
https://codereview.chromium.org/2801603008/diff/1/components/cronet/ios/crone...
> components/cronet/ios/cronet_environment.mm:352:
> DCHECK(base::StatisticsRecorder::IsActive());
> On 2017/04/06 22:08:11, mef wrote:
> > What would happen if they call this on background thread before init
> completes?
> 
> Is there an entry point  (if not CronetEnvironment::Initialize()) which
> guarantees to complete before GetHistogramDeltas() is called?
I don't think so, and I do think that it is a bug.

> On Android, we are doing StatisticsRecorder::Initialize() in JNIOnload() which
> guarantees to be called before the user could do
> CronetEngine.GetHistogramDeltas().

There are similar static constructors and other global initializers that could
be used on iOS, but currently are not.

[xunjieli, 2017-05-15 16:49:38]

Description was changed from

==========
[Cronet iOS] Add base::StatisticsRecorder::IsActive() check

This CL adds a base::StatisticsRecorder::IsActive() check when user calls
GetHistogramDeltas().

BUG=707836
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.android:android_cronet_tester
==========

to

==========
[Cronet iOS] Add base::StatisticsRecorder::IsActive() check

This CL adds a base::StatisticsRecorder::IsActive() check when user calls
GetHistogramDeltas().

BUG=707836
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.android:android_cronet_tester
==========