Fix expected PlacementList sort order.

ui/display/display.cc

 // Copyright (c) 2012 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/display.h"
 
 #include <algorithm>
 
 #include "base/command_line.h"
 #include "base/logging.h"
@@ skipping 41 matching lines @@
       scale_in_double = 1.0;
     }
   }
   return static_cast<float>(scale_in_double);
 }
 
 int64_t internal_display_id_ = -1;
 
 }  // namespace
 
+bool CompareDisplayIds(int64_t id1, int64_t id2) {
+  DCHECK_NE(id1, id2);

[Nico, 2017/07/28 21:09:58]

This DCHECK is not correct. You're passing this to std::sort() which can call
this with the same element for lhs and rhs
(https://stackoverflow.com/questions/38966516/should-sorting-algorithm-pass-sa...).
We're trying to move cros builds to libc++
(https://chromium-review.googlesource.com/c/591775/) and one test fails due to
this incorrect DCHECK. I suppose this should be

  if (id1 == id2) return false;

instead?

+  // Output index is stored in the first 8 bits. See GetDisplayIdFromEDID
+  // in edid_parser.cc.
+  int index_1 = id1 & 0xFF;
+  int index_2 = id2 & 0xFF;
+  DCHECK_NE(index_1, index_2) << id1 << " and " << id2;
+  return Display::IsInternalDisplayId(id1) ||
+         (index_1 < index_2 && !Display::IsInternalDisplayId(id2));
+}
+
 // static
 float Display::GetForcedDeviceScaleFactor() {
   if (g_forced_device_scale_factor < 0)
     g_forced_device_scale_factor = GetForcedDeviceScaleFactorImpl();
   return g_forced_device_scale_factor;
 }
 
 // static
 bool Display::HasForceDeviceScaleFactor() {
   if (g_has_forced_device_scale_factor == -1)
@@ skipping 142 matching lines @@
   DCHECK_NE(kInvalidDisplayId, display_id);
   return HasInternalDisplay() && internal_display_id_ == display_id;
 }
 
 // static
 bool Display::HasInternalDisplay() {
   return internal_display_id_ != kInvalidDisplayId;
 }
 
 }  // namespace display