bindings: Makes almost all attributes accessor-type properties.

Source/modules/cachestorage/CompositorWorkerCacheStorage.idl

Index: Source/modules/cachestorage/CompositorWorkerCacheStorage.idl
diff --git a/Source/modules/cachestorage/WindowCacheStorage.idl b/Source/modules/cachestorage/CompositorWorkerCacheStorage.idl
similarity index 51%
copy from Source/modules/cachestorage/WindowCacheStorage.idl
copy to Source/modules/cachestorage/CompositorWorkerCacheStorage.idl
index 7aadd81083018b278d1624eabf483d4e11ce9e59..0a892fc848cc3a8b0d66a9e14a9f1eb6ddcb646d 100644
--- a/Source/modules/cachestorage/WindowCacheStorage.idl
+++ b/Source/modules/cachestorage/CompositorWorkerCacheStorage.idl
@@ -6,6 +6,12 @@
 [
     RuntimeEnabled=GlobalCacheStorage,
     ImplementedAs=GlobalCacheStorage,
-] partial interface Window {
+] partial interface CompositorWorkerGlobalScope {
+    // Inheritance of [Unforgeable] attributes is not supported.  So we have to
+    // define the same unforgeable attributes in derived interfaces as well.
+    // See that {,Dedicated,Shared,Compositor,Service}WorkerGlobalScope redefine
+    // 'caches' attribute.
+    // Keep all the definitions consistent.
+    // TODO(yukishiino): Support inheritance of attributes defined on instance.
     [Unforgeable, MeasureAs=GlobalCacheStorage, RuntimeEnabled=GlobalCacheStorage, RaisesException] readonly attribute CacheStorage caches;
 };