Add support for virtual displays

ui/display/util/display_util.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/display/util/display_util.h"
 
 #include "base/logging.h"
 
 namespace ui {
 
@@ skipping 50 matching lines @@
     return 1.0f;
 
   const unsigned int dpi = static_cast<unsigned int>(
       kInchInMm * screen_size_in_pixels.width() / physical_size_in_mm.width());
   const unsigned int threshold =
       (physical_size_in_mm.width() >= kLargeDisplayWidthThresholdMM) ?
       kHighDensityDPIThresholdLarge : kHighDensityDPIThresholdSmall;
   return (dpi > threshold) ? 2.0f : 1.0f;
 }
 
+int64_t GenerateDisplayID(uint16_t manufacturer_id,
+                          uint32_t product_code_hash,
+                          uint8_t output_index) {
+  return ((static_cast<int64_t>(manufacturer_id) << 40) |
+          (static_cast<int64_t>(product_code_hash) << 8) | output_index);
+}
+
 }  // namespace ui