the window manger puts SurfaceViews up before they have been
rendered into, because of that surfaceflinger doesn't have
anything ready to draw for that surface when an udpate occurs
and responds by filling the surface with black.
With this fix, we only fill those areas of the framebuffer
that would otherwise be undefined (no content at all).
in the Flash case, the "flash" window is not drawn at all
until it has some content, instead the underlaying browser
window is shown.
Change-Id: Ifb610f7f8c27b88edf83e09adc4803fc295c15a1
179169e88e