blink_gc_plugin: detect singletons with embedded ScriptWrappables.

tools/clang/blink_gc_plugin/Config.h

Index: tools/clang/blink_gc_plugin/Config.h
diff --git a/tools/clang/blink_gc_plugin/Config.h b/tools/clang/blink_gc_plugin/Config.h
index f0c4aeca33bacd8a434dd0048bffe842225abb1d..235bd28be3171aa5f63bad3afc6c3c8e09f3d0c2 100644
--- a/tools/clang/blink_gc_plugin/Config.h
+++ b/tools/clang/blink_gc_plugin/Config.h
@@ -145,6 +145,10 @@ class Config {
            IsGCMixinBase(name);
   }
 
+  static bool IsScriptWrappable(const std::string& name) {
+    return name == "ScriptWrappable";
+  }
+
   static bool IsIterator(const std::string& name) {
     return name == kIteratorName || name == kConstIteratorName ||
            name == kReverseIteratorName || name == kConstReverseIteratorName;
@@ -156,15 +160,16 @@ class Config {
     return IsGCBase(name) || IsRefCountedBase(name);
   }
 
-  static bool IsAnnotated(clang::Decl* decl, const std::string& anno) {
-    clang::AnnotateAttr* attr = decl->getAttr<clang::AnnotateAttr>();
-    return attr && (attr->getAnnotation() == anno);
-  }
+  static bool IsAnnotated(clang::Decl* decl, const std::string& anno);
 
   static bool IsStackAnnotated(clang::Decl* decl) {
     return IsAnnotated(decl, "blink_stack_allocated");
   }
 
+  static bool IsStaticSingleton(clang::Decl* decl) {
+    return IsAnnotated(decl, "blink_gc_singleton_type");
+  }
+
   static bool IsIgnoreAnnotated(clang::Decl* decl) {
     return IsAnnotated(decl, "blink_gc_plugin_ignore");
   }