DevTools: add Tracing agent on back-end

Source/core/inspector/InspectorTracingAgent.h

Index: Source/core/inspector/InspectorTracingAgent.h
diff --git a/Source/core/inspector/InspectorTracingAgent.h b/Source/core/inspector/InspectorTracingAgent.h
new file mode 100644
index 0000000000000000000000000000000000000000..018389cc4f5534e3f0a70a0e1899635730fedfe0
--- /dev/null
+++ b/Source/core/inspector/InspectorTracingAgent.h
@@ -0,0 +1,61 @@
+/*
+ * Copyright 2014 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 InspectorTracingAgent_h
+#define InspectorTracingAgent_h
+
+#include "InspectorFrontend.h"
+#include "core/inspector/InspectorBaseAgent.h"
+#include "wtf/PassOwnPtr.h"
+#include "wtf/text/WTFString.h"
+
+namespace WebCore {
+
+class InspectorClient;
+
+class InspectorTracingAgent FINAL
+    : public InspectorBaseAgent<InspectorTracingAgent>
+    , public InspectorBackendDispatcher::TracingCommandHandler {
+    WTF_MAKE_NONCOPYABLE(InspectorTracingAgent);
+public:
+    static PassOwnPtr<InspectorTracingAgent> create(InspectorClient* client)
+    {
+        return adoptPtr(new InspectorTracingAgent(client));
+    }
+
+    // Base agent methods.
+    virtual void restore() OVERRIDE;
+    virtual void setFrontend(InspectorFrontend*) OVERRIDE;
+    virtual void clearFrontend() OVERRIDE;
+
+
+    // Protocol method implementations.
+    virtual void enable(ErrorString*, const String&) OVERRIDE;
+    virtual void disable(ErrorString*) OVERRIDE;
+    virtual void start(ErrorString*, const String&, const String&, const double*, String* sessionId) OVERRIDE;
+
+
+    // Methods for other agents to use.
+    void startFromBackend();
+    void endFromBackend();
+    void setLayerTreeId(int);
+
+private:
+    explicit InspectorTracingAgent(InspectorClient*);
+
+    void innerStart();
+    void emitMetadataEvents();
+    String sessionId();
+
+    InspectorFrontend::Tracing* m_frontend;
+    InspectorClient* m_client;
+    bool m_shouldStopTracing;
+    int m_layerTreeId;
+};
+
+}
+
+#endif // InspectorTracingAgent_h