Collect host of Web Component usage to send to RAPPOR

Source/core/frame/OriginsUsingFeatures.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 OriginsUsingFeatures_h
+#define OriginsUsingFeatures_h
+
+#include "platform/heap/Handle.h"
+#include "wtf/Vector.h"
+#include "wtf/text/WTFString.h"
+
+namespace blink {
+
+class Document;
+class ScriptState;
+
+class OriginsUsingFeatures {
+    DISALLOW_ALLOCATION();
+public:
+    ~OriginsUsingFeatures();
+
+    enum class Feature {
+        ElementCreateShadowRoot,
+        DocumentRegisterElement,
+
+        NumberOfFeatures // This must be the last item.
+    };
+
+    static void count(const ScriptState*, Document&, Feature);
+
+    void documentDetached(Document&);
+    void updateMeasurementsAndClear();
+
+    class Value {
+    public:
+        Value();
+
+        bool isEmpty() const { return !m_countBits; }
+        void clear() { m_countBits = 0; }
+
+        void count(Feature);
+        bool get(Feature feature) const { return m_countBits & (1 << static_cast<unsigned>(feature)); }
+
+        void aggregate(Value);
+        void updateMeasurements(const String& origin);
+
+    private:
+        unsigned m_countBits : static_cast<unsigned>(Feature::NumberOfFeatures);
+    };
+
+private:
+    Vector<std::pair<String, OriginsUsingFeatures::Value>, 1> m_originAndValues;
+};
+
+} // namespace blink
+
+#endif // OriginsUsingFeatures_h