fix crash when validating an invalid EGL objects

the code that validated EGL objects dereferenced the object
to access its EGLDisplay -- needed for validation (!).
This was wrong for two reasons, first we dereferenced the object
before validating it (potentially leading to a crash), secondly
we didn't validate that the object existed in the right EGLDisplay.

We now use the EGLDisplay passed by the user API.

Change-Id: I66f9e851d4f8507892a6b1fee3065f124c4e7138
diff --git a/opengl/libs/EGL/egl_display.cpp b/opengl/libs/EGL/egl_display.cpp
index 558ca77..2935832 100644
--- a/opengl/libs/EGL/egl_display.cpp
+++ b/opengl/libs/EGL/egl_display.cpp
@@ -62,11 +62,13 @@
     objects.remove(object);
 }
 
-bool egl_display_t::getObject(egl_object_t* object) {
+bool egl_display_t::getObject(egl_object_t* object) const {
     Mutex::Autolock _l(lock);
     if (objects.indexOf(object) >= 0) {
-        object->incRef();
-        return true;
+        if (object->getDisplay() == this) {
+            object->incRef();
+            return true;
+        }
     }
     return false;
 }