WebEngine may fail to create context for a view if many are open already

Should be reproducible on at least some machines with WebEngine Demo Browser example. Attached qtdiag output is from a machine where this happens at around 11 tabs.

To reproduce:

• Run WebEngine Demo Browser example
• Open a lot of websites

What could happen:

• page is not rendered, but seems to work otherwise and this is printed to application output:

  ARB::createContext: wglCreateContextAttribsARB() failed (GL error code: 0x500)
  for format: QSurfaceFormat(version 2.0, options QFlags(), depthBufferSize 24,
  redBufferSize -1, greenBufferSize -1, blueBufferSize -1, alphaBufferSize -1,
  stencilBufferSize 8, samples 0, swapBehavior 0, swapInterval 1, profile 0),
  shared context: 0x20001 ()
  
  GDI::createContext: wglShareLists() failed. ()
  
  ARB::createContext: wglCreateContextAttribsARB() failed (GL error code: 0x0)
  for format: QSurfaceFormat(version 2.0, options QFlags(), depthBufferSize 24,
  redBufferSize -1, greenBufferSize -1, blueBufferSize -1, alphaBufferSize -1,
  stencilBufferSize 8, samples 0, swapBehavior 0, swapInterval 1, profile 0),
  shared context: 0x20001 ()
  
  GDI::createContext: wglShareLists() failed. ()