[ozone] Enable display controller before notifying its users that it's available.

ui/ozone/platform/dri/screen_manager.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/ozone/platform/dri/screen_manager.h"
 
 #include <xf86drmMode.h>
 
 #include "third_party/skia/include/core/SkCanvas.h"
 #include "ui/gfx/geometry/point.h"
@@ skipping 103 matching lines @@
       origin == controller->origin()) {
     if (controller->IsDisabled()) {
       HardwareDisplayControllers::iterator mirror =
           FindActiveDisplayControllerByLocation(modeset_bounds);
       // If there is an active controller at the same location then start mirror
       // mode.
       if (mirror != controllers_.end())
         return HandleMirrorMode(it, mirror, crtc, connector);
     }
 
+    // Just re-enable the controller to re-use the current state.
+    bool enabled = controller->Enable();
     FOR_EACH_OBSERVER(DisplayChangeObserver, observers_,
                       OnDisplayChanged(controller));
-    // Just re-enable the controller to re-use the current state.
-    return controller->Enable();
+
+    return enabled;
   }
 
   // Either the mode or the location of the display changed, so exit mirror
   // mode and configure the display independently. If the caller still wants
   // mirror mode, subsequent calls configuring the other controllers will
   // restore mirror mode.
   if (controller->IsMirrored()) {
     controller = new HardwareDisplayController(controller->RemoveCrtc(crtc));
     controllers_.push_back(controller);
     it = controllers_.end() - 1;
@@ skipping 142 matching lines @@
 
   // When things go wrong revert back to the previous configuration since
   // it is expected that the configuration would not have changed if
   // things fail.
   (*original)->AddCrtc((*mirror)->RemoveCrtc(crtc));
   (*original)->Enable();
   return false;
 }
 
 }  // namespace ui