Fix retrieving the current Display.

eglGetCurrentDisplay() returned a pointer to the concrete egl::Display
object, instead of the opaque identifier obtained from eglGetDisplay.
This was a regression caused by
https://swiftshader-review.googlesource.com/10188

Bug chromium:738298

Change-Id: Id3a87fc3978f8f4efdc77d6c5eaa85743fa3672c
Reviewed-on: https://swiftshader-review.googlesource.com/10508
Tested-by: Nicolas Capens <capn@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>

src/OpenGL/libEGL/libEGL.cpp

diff --git a/src/OpenGL/libEGL/libEGL.cpp b/src/OpenGL/libEGL/libEGL.cpp
index c7a4127..3a62da0 100644
--- a/src/OpenGL/libEGL/libEGL.cpp
+++ b/src/OpenGL/libEGL/libEGL.cpp
@@ -862,7 +862,14 @@
 		return success(EGL_NO_DISPLAY);
 	}
 
-	return success(context->getDisplay());
+	egl::Display *display = context->getDisplay();
+
+	if(!display)
+	{
+		return error(EGL_BAD_ACCESS, EGL_NO_DISPLAY);
+	}
+
+	return success(display->getEGLDisplay());
 }
 
 EGLBoolean QueryContext(EGLDisplay dpy, EGLContext ctx, EGLint attribute, EGLint *value)