Fix crash on item drag in shelf.

chrome/browser/ui/ash/launcher/chrome_launcher_controller_impl_unittest.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 "chrome/browser/ui/ash/launcher/chrome_launcher_controller_impl.h"
 
 #include <stddef.h>
 
 #include <algorithm>
 #include <map>
@@ skipping 3896 matching lines @@
   EXPECT_TRUE(launcher_controller_->GetArcDeferredLauncher()->HasApp(app_id));
 
   std::string window_app_id("org.chromium.arc.1");
   CreateArcWindow(window_app_id);
   arc_test_.app_instance()->SendTaskCreated(1,
                                             arc_test_.fake_default_apps()[0]);
 
   EXPECT_NE(0, launcher_controller_->GetShelfIDForAppID(app_id));
   EXPECT_FALSE(launcher_controller_->GetArcDeferredLauncher()->HasApp(app_id));
 }
+
+// Checks the case when several app items have the same ordinal position (which
+// is valid case).
+TEST_F(ChromeLauncherControllerImplTest, CheckPositionConflict) {
+  InitLauncherController();
+
+  extension_service_->AddExtension(extension1_.get());
+  extension_service_->AddExtension(extension2_.get());
+  extension_service_->AddExtension(extension3_.get());
+  extension_service_->AddExtension(extension4_.get());
+
+  syncer::SyncChangeList sync_list;
+  InsertAddPinChange(&sync_list, 0, extension_misc::kChromeAppId);
+  InsertAddPinChange(&sync_list, 1, extension1_->id());
+  InsertAddPinChange(&sync_list, 1, extension2_->id());
+  InsertAddPinChange(&sync_list, 1, extension3_->id());
+  SendPinChanges(sync_list, true);
+
+  EXPECT_EQ("AppList, Chrome, App1, App2, App3", GetPinnedAppStatus());
+
+  const syncer::StringOrdinal position_chrome =
+      app_service_->GetPinPosition(extension_misc::kChromeAppId);
+  const syncer::StringOrdinal position_1 =
+      app_service_->GetPinPosition(extension1_->id());
+  const syncer::StringOrdinal position_2 =
+      app_service_->GetPinPosition(extension2_->id());
+  const syncer::StringOrdinal position_3 =
+      app_service_->GetPinPosition(extension3_->id());
+  EXPECT_TRUE(position_chrome.LessThan(position_1));
+  EXPECT_TRUE(position_1.Equals(position_2));
+  EXPECT_TRUE(position_2.Equals(position_3));
+
+  // Move Chrome between App1 and App2.
+  // Note, move target_index is in context when moved element is removed from
+  // array first.
+  model_->Move(1, 2);
+  EXPECT_EQ("AppList, App1, Chrome, App2, App3", GetPinnedAppStatus());
+
+  // Expect sync positions for Chrome, App2, App3 are updated.
+  const syncer::StringOrdinal position_chrome_a =
+      app_service_->GetPinPosition(extension_misc::kChromeAppId);
+  const syncer::StringOrdinal position_1_a =
+      app_service_->GetPinPosition(extension1_->id());
+  const syncer::StringOrdinal position_2_a =
+      app_service_->GetPinPosition(extension2_->id());
+  const syncer::StringOrdinal position_3_a =
+      app_service_->GetPinPosition(extension3_->id());
+  EXPECT_TRUE(position_1.Equals(position_1_a));
+  EXPECT_TRUE(position_1_a.LessThan(position_chrome_a));
+  EXPECT_TRUE(position_chrome_a.LessThan(position_2_a));
+  EXPECT_TRUE(position_2_a.LessThan(position_3_a));
+}