Bug 200904

The accelerated video-to-WebGL-texture upload path in Source/WebCore/platform/graphics/cv/VideoTextureCopierCV.cpp and related files is currently #ifdef'd out for the ANGLE backend for WebGL. From examining the code and after discussion with Geoff Lang and Jamie Madill from the ANGLE team, in order to implement it, it seems a few changes will be necessary: (these are only for desktop GL; more work will be needed for iOS and OpenGL ES): 1) A new ANGLE extension needs to be defined to expose the CGLContextObj and CGLPixelFormatObj associated with the EGLDisplay. 2) A new ANGLE extension needs to be defined to allow creation of a pbuffer from a client buffer which is actually a driver-level OpenGL texture ID. 3) TextureCacheCV will need to be changed to allocate a separate OpenGL context sharing resources with ANGLE's, and allocate the CVOpenGLTextureCacheCreate with that separate context. textureFromImage will get the native texture from the CVOpenGLTextureCache and import it into ANGLE's context as a pbuffer, then bind it to a texture ANGLE can reference. At that point, the rest of the code in VideoTextureCopierCV should be able to operate against the texture in ANGLE's context. Some of the shaders may need to be ported to use ANGLE's rectangular texture extensions. This bug might end up being a meta-bug, since at least one ANGLE roll will be needed for the above changes. There's also an IOSurface code path in VideoTextureCopierCV::copyImageToPlatformTexture; I haven't figured out whether that's usually taken and whether it's important to implement.