Implement eglQueryContext.

Bug b/37991302

Change-Id: I8a1c28d4a9c8968be3a04da64a19ddd3f5274dd6
Reviewed-on: https://swiftshader-review.googlesource.com/9768
Tested-by: Nicolas Capens <capn@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <capn@google.com>
diff --git a/src/OpenGL/libEGL/libEGL.cpp b/src/OpenGL/libEGL/libEGL.cpp
index 4a1998f..3103abf 100644
--- a/src/OpenGL/libEGL/libEGL.cpp
+++ b/src/OpenGL/libEGL/libEGL.cpp
@@ -871,9 +871,25 @@
 		return EGL_FALSE;
 	}
 
-	UNIMPLEMENTED();   // FIXME
+	switch(attribute)
+	{
+	case EGL_CONFIG_ID:

+		*value = context->getConfigID();

+		break;

+	case EGL_CONTEXT_CLIENT_TYPE:

+		*value = egl::getCurrentAPI();

+		break;

+	case EGL_CONTEXT_CLIENT_VERSION:
+		*value = context->getClientVersion();
+		break;
+	case EGL_RENDER_BUFFER:
+		*value = EGL_BACK_BUFFER;

+		break;
+	default:
+		return error(EGL_BAD_ATTRIBUTE, EGL_FALSE);
+	}
 
-	return success(0);
+	return success(EGL_TRUE);
 }
 
 EGLBoolean WaitGL(void)