log an error when eglCreateContext() fails in an inconsistant way

this will help debugging bug: 7216919

Change-Id: I54ac65f20c5ed55cc93a5cbc5350fadfb0fcb804

opengl/libs/EGL/eglApi.cpp

@@ -416,6 +416,12 @@ EGLContext eglCreateContext(EGLDisplay dpy, EGLConfig config,
                 GLTrace_eglCreateContext(version, c);
 #endif
             return c;
+        } else {
+            EGLint error = eglGetError();
+            ALOGE_IF(error == EGL_SUCCESS,
+                    "eglCreateContext(%p, %p, %p, %p) returned EGL_NO_CONTEXT "
+                    "but no EGL error!",
+                    dpy, config, share_list, attrib_list);
         }
     }
     return EGL_NO_CONTEXT;