Removing VR screen buffer in Gecko

[daoshengmu]

Current Behavior

We currently ask for an additional buffer to get the AndroidSurfaceTexture from WebGL context. It looks like the gl->Screen() is already been copied the frame result from WebGL framebuffer. We should just use it.

Expected Behavior

Remove VR screen buffer, just us gl->Screen(). I have filed Bug 1558333 to work on.

Possible Solution

Context

Error Logs and Stack Traces

[philip-lamb]

@daoshengmu Let's chat about the relationship between this bug and the work tracked in https://bugzilla.mozilla.org/show_bug.cgi?id=1537961

[daoshengmu]

@daoshengmu Let's chat about the relationship between this bug and the work tracked in https://bugzilla.mozilla.org/show_bug.cgi?id=1537961

According to the review comment at https://phabricator.services.mozilla.com/D34435. It still has some concerns about deadlocks (WebVR using the same texture at the same time of compositor). Therefore, I think we can close this issue, and the following works will be #1429.

[jvonitter]

thanks @daoshengmu !