[Qtwebengine] Notice: The qtwebengine master build is currently broken with latest stable qtdeclarative

[Jocelyn Turcotte]

Hello,

https://codereview.qt-project.org/82541 just landed and should make its
way toward qt5.git's stable soon. It was slightly rushed-in to make sure
that it lands before Qt stable is merged to the 5.3 release branch.

If you try to build qtwebengine master with a build of qtdeclarative
containing this change, you'll get a build error about
QSGContext::sharedOpenGLContext not being declared.

The following changes will fix the build with Qt stable once landed:
https://codereview.qt-project.org/82540
https://codereview.qt-project.org/82721
https://codereview.qt-project.org/82722

Meanwhile, please either use an older checkout of qtdeclarative stable,
revert the first mentioned change, or cherry-pick the 3 later mentioned
changes.

Cheers,
Jocelyn