Revert of Migrate BrowserAccessibility windows unique id handling to AXPlatformNodeWin.

ui/accessibility/platform/ax_platform_node.cc

Index: ui/accessibility/platform/ax_platform_node.cc
diff --git a/ui/accessibility/platform/ax_platform_node.cc b/ui/accessibility/platform/ax_platform_node.cc
index b35ecb956006ba35656cb0d34f457399f9c042c8..93a374abbacd9dd610e47b1aa8d1dd64803fbe17 100644
--- a/ui/accessibility/platform/ax_platform_node.cc
+++ b/ui/accessibility/platform/ax_platform_node.cc
@@ -9,15 +9,39 @@
 #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