WebStateList is an array of web::WebState* wrappers.

ios/shared/chrome/browser/tabs/BUILD.gn

Index: ios/shared/chrome/browser/tabs/BUILD.gn
diff --git a/ios/shared/chrome/browser/tabs/BUILD.gn b/ios/shared/chrome/browser/tabs/BUILD.gn
new file mode 100644
index 0000000000000000000000000000000000000000..834cbc250c5e087c432c70fdc10a8d660761ee1f
--- /dev/null
+++ b/ios/shared/chrome/browser/tabs/BUILD.gn
@@ -0,0 +1,16 @@
+# Copyright 2017 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.
+
+source_set("tabs") {
+  sources = [
+    "web_state_handle.h",
+    "web_state_list.h",
+    "web_state_list.mm",
+  ]
+  deps = [
+    "//base",
+  ]
+  libs = [ "Foundation.framework" ]
+  configs += [ "//build/config/compiler:enable_arc" ]
+}