Revert of Migrate BrowserAccessibility windows unique id handling to AXPlatformNodeWin.

ui/accessibility/platform/ax_platform_node.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/accessibility/platform/ax_platform_node.h"
 
 #include "base/containers/hash_tables.h"
 #include "base/lazy_instance.h"
 #include "build/build_config.h"
 #include "ui/accessibility/ax_node_data.h"
 #include "ui/accessibility/platform/ax_platform_node_delegate.h"
+#include "ui/accessibility/platform/ax_platform_unique_id.h"
 
 namespace ui {
 
-AXPlatformNode::AXPlatformNode() {}
+namespace {
+
+using UniqueIdMap = base::hash_map<int32_t, AXPlatformNode*>;
+// Map from each AXPlatformNode's unique id to its instance.
+base::LazyInstance<UniqueIdMap>::DestructorAtExit g_unique_id_map =
+    LAZY_INSTANCE_INITIALIZER;
+}
+
+AXPlatformNode::AXPlatformNode() : unique_id_(GetNextAXPlatformNodeUniqueId()) {
+  g_unique_id_map.Get()[unique_id_] = this;
+}
 
 AXPlatformNode::~AXPlatformNode() {
+  if (unique_id_)
+    g_unique_id_map.Get().erase(unique_id_);
 }
 
 void AXPlatformNode::Destroy() {
+  g_unique_id_map.Get().erase(unique_id_);
+  unique_id_ = 0;
+}
+
+AXPlatformNode* AXPlatformNode::GetFromUniqueId(int32_t unique_id) {
+  UniqueIdMap* unique_ids = g_unique_id_map.Pointer();
+  auto iter = unique_ids->find(unique_id);
+  if (iter != unique_ids->end())
+    return iter->second;
+
+  return nullptr;
 }
 
 }  // namespace ui