Use unique IDs for accessibility nodes on Android

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 8f889458ddb28af0c6334f6577233b0ecdc44b16..adfcc1e2ad2f2059b4f9d299242e7378e19fcc0c 100644
--- a/ui/accessibility/platform/ax_platform_node.cc
+++ b/ui/accessibility/platform/ax_platform_node.cc
@@ -4,12 +4,23 @@
 
 #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"
 
 namespace ui {
 
+namespace {
+
+using UniqueIdMap = base::hash_map<int32_t, AXPlatformNode*>;
+// Map from each AXPlatformNode's unique id to its instance.
+base::LazyInstance<UniqueIdMap> g_unique_id_map =
+    LAZY_INSTANCE_INITIALIZER;
+
+}
+
 #if !defined(PLATFORM_HAS_AX_PLATFORM_NODE_IMPL)
 // static
 AXPlatformNode* AXPlatformNode::Create(AXPlatformNodeDelegate* delegate) {
@@ -28,10 +39,39 @@ AXPlatformNode* AXPlatformNode::FromNativeViewAccessible(
 }
 #endif
 
-AXPlatformNode::AXPlatformNode() {
+// static
+int32_t AXPlatformNode::GetNextUniqueId() {
+  static int32_t next_unique_id = 1;
+  int32_t unique_id = next_unique_id;
+  if (next_unique_id == INT32_MAX)
+    next_unique_id = 1;
+  else
+    next_unique_id++;
+
+  return unique_id;
+}
+
+AXPlatformNode::AXPlatformNode() : unique_id_(GetNextUniqueId()) {
+  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