blink_gc_plugin: detect singletons with embedded ScriptWrappables.

tools/clang/blink_gc_plugin/tests/static_singleton.cpp

Index: tools/clang/blink_gc_plugin/tests/static_singleton.cpp
diff --git a/tools/clang/blink_gc_plugin/tests/static_singleton.cpp b/tools/clang/blink_gc_plugin/tests/static_singleton.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..80eb034c1417faa01abf4d01cf93cccbe62c468f
--- /dev/null
+++ b/tools/clang/blink_gc_plugin/tests/static_singleton.cpp
@@ -0,0 +1,37 @@
+// 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.
+
+#include "static_singleton.h"
+
+#define DEFINE_STATIC_LOCAL(Type, Name) \
+  BLINK_STATIC_SINGLETON()              \
+  static Persistent<Type> Name(new Type)
+
+namespace blink {
+
+HeapObject& HeapObject::instance() {
+  DEFINE_STATIC_LOCAL(HeapObject, object);
+  return *object;
+}
+
+namespace {
+
+HeapObject& instance(int i) {
+  if (i > 2) {
+    DEFINE_STATIC_LOCAL(HeapObject, object);
+    return *object;
+  }
+  DEFINE_STATIC_LOCAL(HeapObject, object);
+  return *object;
+}
+
+HeapObject& instance_ignored() {
+  GC_PLUGIN_IGNORE("")
+  DEFINE_STATIC_LOCAL(HeapObject, object);
+  return *object;
+}
+
+}  // namespace
+
+}  // namespace blink