Added a system caret used for accessibility on Windows.

ui/accessibility/BUILD.gn

Index: ui/accessibility/BUILD.gn
diff --git a/ui/accessibility/BUILD.gn b/ui/accessibility/BUILD.gn
index 5c49e120543e3fef2d11906ecb4d6c770c3afecf..f48fc476061a592ac0f783cfc1aca1adadabf8a9 100644
--- a/ui/accessibility/BUILD.gn
+++ b/ui/accessibility/BUILD.gn
@@ -137,6 +137,7 @@ if (is_android) {
 }
 
 static_library("test_support") {
+  testonly = true
   sources = [
     "tree_generator.cc",
     "tree_generator.h",
@@ -155,6 +156,7 @@ static_library("test_support") {
 }
 
 test("accessibility_unittests") {
+  testonly = true
   sources = [
     "ax_generated_tree_unittest.cc",
     "ax_node_position_unittest.cc",
@@ -162,6 +164,7 @@ test("accessibility_unittests") {
     "ax_tree_combiner_unittest.cc",
     "ax_tree_serializer_unittest.cc",
     "ax_tree_unittest.cc",
+    "platform/ax_fake_caret_win_interactive_uitest.cc",
     "platform/ax_platform_node_win_unittest.cc",
   ]
 
@@ -179,7 +182,11 @@ test("accessibility_unittests") {
   ]
 
   if (is_win) {
-    deps += [ "//third_party/iaccessible2" ]
+    deps += [
+      "//third_party/iaccessible2",
+      "//ui/views/:test_support",
+    ]
+    libs = [ "oleacc.lib" ]
   }
 }