AMD provides http://developer.amd.com/tools-and-sdks/graphics-development/amd-opengl-es-sdk/ (libEGL / libGLESv2). For ATI Radeon HD 5400 Series and Catalist 13.1 eglGetProcAddress("glBlitFramebufferANGLE") and eglGetProcAddress("glRenderbufferStorageMultisampleANGLE") return valid addresses (from atio6axx.dll!). These results are used to check whether it's ANGLE implementation. As result it works only if angle is enabled. I think that AMD's implementation should be treated separately.
Thank you Dmytro! So how can we properly identify a buggy ANGLE impl. (issues w/ Chrome etc) ? Also nice to see those *EGL* lib being exposed. We have to re-align our GL backend, i.e. allow EGL to be used for desktop profiles as well. But thats another story.