Update ANGLE docs to match MakeCurrent status

MakeCurrent no longer generates EGL_BAD_SURFACE when the pbuffers are
IOSurfaces. So the documentation has been updated to match.

Bug chromium:987289

Change-Id: Id074d9d6d8d0a50c91ec725ec2016a4f5ad4b6e4
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/34568
Presubmit-Ready: Sean Risser <srisser@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Tested-by: Sean Risser <srisser@google.com>
diff --git a/extensions/EGL_ANGLE_iosurface_client_buffer.txt b/extensions/EGL_ANGLE_iosurface_client_buffer.txt
index 692f721..85daac2 100644
--- a/extensions/EGL_ANGLE_iosurface_client_buffer.txt
+++ b/extensions/EGL_ANGLE_iosurface_client_buffer.txt
@@ -21,7 +21,7 @@
 
 Version
 
-    Version 1, Dec 6, 2017
+    Version 2, Aug 1, 2019
 
 Number
 
@@ -108,11 +108,6 @@
     of the associcated IOSurface object are undefined while the pbuffer is
     bound to a client texture."
 
-    Append to the list of errors generated by eglMakeCurrent in Section 3.7.3:
-    "  - If either draw or read are pbuffers created with
-    eglCreatePbufferFromClientBuffer with <buftype> set to EGL_IOSURFACE_ANGLE,
-    an EGL_BAD_SURFACE is generated."
-
 Issues
 
     There are no issues, please move on.
@@ -120,3 +115,4 @@
 Revision History
 
     Version 1, 2017/12/06 - first draft.
+    Version 2, 2019/08/01 - allow MakeCurrent