CachedMetadata support for ServiceWorker script.

Source/core/fetch/CachedMetadataHandler.h

+// Copyright 2015 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.
+
+#ifndef CachedMetadataHandler_h
+#define CachedMetadataHandler_h
+
+#include "wtf/Forward.h"
+
+namespace blink {
+
+class CachedMetadata;
+
+// Handler class for caching operations.
+class CachedMetadataHandler {
+public:
+    enum CacheType {
+        SendToPlatform, // send cache data to blink::Platform::cacheMetadata
+        CacheLocally // cache only in Resource's member variables
+    };
+    virtual ~CachedMetadataHandler() { }
+    // Caches the given metadata in association with this resource and suggests
+    // that the platform persist it. The dataTypeID is a pseudo-randomly chosen
+    // identifier that is used to distinguish data generated by the caller.
+    virtual void setCachedMetadata(unsigned dataTypeID, const char*, size_t, CacheType = SendToPlatform) = 0;
+    // Reset existing metadata, to allow setting new data.
+    virtual void clearCachedMetadata(CacheType = CacheLocally) = 0;
+    // Returns cached metadata of the given type associated with this resource.
+    virtual CachedMetadata* cachedMetadata(unsigned dataTypeID) const = 0;
+    // Returns the encoding to which the cache is specific.
+    virtual String encoding() const = 0;
+
+protected:
+    CachedMetadataHandler() { }
+};
+}
+
+#endif // CachedMetadataHandler_h