[Ozone-DRI] Reuse framebuffer when re-enabling CRTC

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 91 matching lines @@
                            mode.vdisplay);
   HardwareDisplayControllers::iterator it = FindDisplayController(crtc);
   DCHECK(controllers_.end() != it) << "Display controller (crtc=" << crtc
                                    << ") doesn't exist.";
 
   HardwareDisplayController* controller = *it;
   controller = *it;
   // If nothing changed just enable the controller. Note, we perform an exact
   // comparison on the mode since the refresh rate may have changed.
   if (SameMode(mode, controller->get_mode()) &&
-      origin == controller->origin() && !controller->IsDisabled())
+      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.
     return controller->Enable();
+  }
 
   // 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 127 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