Allow moving cursors between connected displays.

ash/display/display_layout_store.cc

 // Copyright 2013 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 <stdio.h>
 
 #include "ash/ash_switches.h"
 #include "ash/display/display_layout_store.h"
 #include "ash/display/display_manager.h"
 #include "ash/display/display_util.h"
@@ skipping 32 matching lines @@
 void DisplayLayoutStore::SetDefaultDisplayPlacement(
     const DisplayPlacement& placement) {
   base::CommandLine* command_line = base::CommandLine::ForCurrentProcess();
   if (!command_line->HasSwitch(switches::kAshSecondaryDisplayLayout))
     default_display_placement_ = placement;
 }
 
 void DisplayLayoutStore::RegisterLayoutForDisplayIdList(
     const DisplayIdList& list,
     scoped_ptr<DisplayLayout> layout) {
+  // A dev/beta channel may have a bad layout data saved in local state.

[stevenjb, 2016/03/24 18:08:29]

nit: s/a bad/bad/

[oshima, 2016/03/24 20:37:19]

Done.

+  // TODO(oshima): Consider removing this a coulpe of milestones later.

[stevenjb, 2016/03/24 18:08:29]

nit: /a couple of milestones later/after M52/ (or 53)

[oshima, 2016/03/24 20:37:19]

Done.

+  if (list.size() == 2 && layout->placement_list.size() > 1)
+    return;
 
   // Do not overwrite the valid data with old invalid date.
   if (layouts_.count(list) && !CompareDisplayIds(list[0], list[1]))
     return;
 
   // Old data may not have the display_id/parent_display_id.
   // Guess these values based on the saved primary_id.
   if (layout->placement_list.size() >= 1 &&
       layout->placement_list[0].display_id == gfx::Display::kInvalidDisplayID) {
     if (layout->primary_id == list[1]) {
       layout->placement_list[0].display_id = list[0];
       layout->placement_list[0].parent_display_id = list[1];
     } else {
       layout->placement_list[0].display_id = list[1];
       layout->placement_list[0].parent_display_id = list[0];
     }
   }
-  DCHECK(DisplayLayout::Validate(list, *layout.get())) << layout->ToString();
+  DCHECK(DisplayLayout::Validate(list, *layout.get()))
+      << "ids=" << DisplayIdListToString(list)
+      << ", layout=" << layout->ToString();
   layouts_[list] = std::move(layout);
 }
 
 const DisplayLayout& DisplayLayoutStore::GetRegisteredDisplayLayout(
     const DisplayIdList& list) {
   DCHECK_NE(1u, list.size());
   const auto iter = layouts_.find(list);
   const DisplayLayout* layout = iter != layouts_.end()
                                     ? iter->second.get()
                                     : CreateDefaultDisplayLayout(list);
@@ skipping 24 matching lines @@
     placement.display_id = list[i + 1];
     placement.parent_display_id = list[i];
     layout->placement_list.push_back(placement);
   }
   layouts_[list] = std::move(layout);
   auto iter = layouts_.find(list);
   return iter->second.get();
 }
 
 }  // namespace ash