Reland: ash: reset color management when new screens are hotplugged

ash/display/display_color_manager_chromeos.cc

 // Copyright 2015 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 "ash/display/display_color_manager_chromeos.h"
 
 #include <utility>
 
 #include "base/bind.h"
 #include "base/files/file_util.h"
@@ skipping 145 matching lines @@
   configurator_->AddObserver(this);
 }
 
 DisplayColorManager::~DisplayColorManager() {
   configurator_->RemoveObserver(this);
   STLDeleteValues(&calibration_map_);
 }
 
 void DisplayColorManager::OnDisplayModeChanged(
     const ui::DisplayConfigurator::DisplayStateList& display_states) {
+  ColorCalibrationData reset_calibration;
+
   for (const ui::DisplaySnapshot* state : display_states) {
+    // Ensure we always reset the configuration before setting a new one.
+    configurator_->SetColorCorrection(
+        state->display_id(), reset_calibration.degamma_lut,

[robert.bradford, 2016/04/27 12:29:46]

Don't use the ColorCalibrationData to just get three empty vectors. If you want
to just have empty vectors just create 3 empty vectors.

I need more convincing that using empty vectors is more than a hack here :-)

You're also setting this even if the platform doesn't support display color
management.

+        reset_calibration.gamma_lut, reset_calibration.correction_matrix);
+
     if (calibration_map_[state->product_id()]) {
       ApplyDisplayColorCalibration(state->display_id(), state->product_id());
     } else {
       if (state->product_id() != ui::DisplaySnapshot::kInvalidProductID)
         LoadCalibrationForDisplay(state);
     }
   }
 }
 
 void DisplayColorManager::ApplyDisplayColorCalibration(int64_t display_id,
@@ skipping 66 matching lines @@
     calibration_map_[product_id] = data.release();
     ApplyDisplayColorCalibration(display_id, product_id);
   }
 }
 
 DisplayColorManager::ColorCalibrationData::ColorCalibrationData() {}
 
 DisplayColorManager::ColorCalibrationData::~ColorCalibrationData() {}
 
 }  // namespace ash