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.h b/opengl/libs/EGL/egl_display.h
index e0a367d..94077be 100644
--- a/opengl/libs/EGL/egl_display.h
+++ b/opengl/libs/EGL/egl_display.h
@@ -81,7 +81,7 @@
     // remove object from this display's list
     void removeObject(egl_object_t* object);
     // add reference to this object. returns true if this is a valid object.
-    bool getObject(egl_object_t* object);
+    bool getObject(egl_object_t* object) const;
 
 
     static egl_display_t* get(EGLDisplay dpy);
@@ -119,9 +119,9 @@
     egl_config_t*   configs;
 
 private:
-    uint32_t        refs;
-    Mutex           lock;
-    SortedVector<egl_object_t*> objects;
+            uint32_t                    refs;
+    mutable Mutex                       lock;
+            SortedVector<egl_object_t*> objects;
 };
 
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