1343383 - nsIDOMWindowUtils::StartFrameTimeRecording should not use sync IPC

Status: NEW

(Core :: Graphics: Layers, defect, P3)

Description

[Markus Stange [:mstange]]

We use this for recording tab opening telemetry when the user has opted in to extended telemetry recording.

http://searchfox.org/mozilla-central/rev/9c1c7106eef137e3413fd867fc1ddfb1d3f6728c/browser/base/content/tabbrowser.xml#6297

Comment 1

[Milan Sreckovic [:milan] (needinfo for best results)]

Naveed, p1 even though this is a non-default extended telemetry setting?  Do we know what percentage of our release population sets that?  Or do we need this because it's blocking our profiling in some way?

Comment 2

[Naveed Ihsanullah [:naveed]]

Changed to [qf:p3] after talking it over with mstange.

Comment 3

[Markus Stange [:mstange]]

Plan:
 1. Move the implementation of Start/StopFrameTimeRecording out of the LayerManager base class and into LayerManagerComposite.
 2. Rename the argument aStartIndex into aHandle.
 3. Make StopFrameTimeRecording return a MozPromise instead.
 4. Make nsDOMWindowUtils turn that MozPromise into a DOM promise and adjust both the tabbrowser.xml caller and Talos.
 5. Add a counter uint32_t mNextFrameTimeRecordingHandle to ClientLayerManager.
 6. Make ClientLayerManager pass that ID to the IPDL method StartFrameTimeRecording and make it async that method. (Instead of awaiting a handle in the return value, the handle is now decided by the caller.) On the other side (in CompositorBridgeParent), create a map from frameTimeRecordingHandle -> handleThatWasReturnedByLayerManagerComposite. When CompositorBridgeParent::RecvStopFrameTimeRecording is called, look up the right handle and call LayerManagerComposite::StopFrameTimeRecording with it.
 7. Turn PCompositorBridge::StopFrameTimeRecording into an "async return" IPDL method that returns the array using MozPromise, and hook up the promises correctly.

Comment 4

[Markus Stange [:mstange]]

This API is no longer used during tab opening, bug 1345315 removed the call.

The only remaining user is the TART talos test.

Comment 5

[Markus Stange [:mstange]]

I'm not working on this.