Avoid exposing cc::Layer tree to CompositorProxy

third_party/WebKit/Source/core/dom/CompositorProxy.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 CompositorProxy_h
 #define CompositorProxy_h
 
 #include "bindings/core/v8/ScriptWrappable.h"
 #include "core/CoreExport.h"
 #include "core/dom/CompositorProxyClient.h"
@@ skipping 20 matching lines @@
                                  const Vector<String>& attributeArray,
                                  ExceptionState&);
   static CompositorProxy* create(ExecutionContext*,
                                  uint64_t element,
                                  uint32_t compositorMutableProperties);
   virtual ~CompositorProxy();
 
   DEFINE_INLINE_TRACE() {}
 
   uint64_t elementId() const { return m_elementId; }
+  uint64_t proxyId() const { return m_proxyId; }
   uint32_t compositorMutableProperties() const {
     return m_compositorMutableProperties;
   }
   bool supports(const String& attribute) const;
 
   bool initialized() const { return m_connected && m_state.get(); }
   bool connected() const { return m_connected; }
   void disconnect();
 
   double opacity(ExceptionState&) const;
@@ skipping 14 matching lines @@
   CompositorProxy(uint64_t element,
                   uint32_t compositorMutableProperties,
                   CompositorProxyClient*);
 
  private:
   bool raiseExceptionIfNotMutable(uint32_t compositorMutableProperty,
                                   ExceptionState&) const;
   void disconnectInternal();
 
   const uint64_t m_elementId = 0;
+  const uint64_t m_proxyId = 0;

[flackr, 2017/04/03 17:09:19]

Do we need proxyId? Can we not key off of elementId?

[smcgruer, 2017/04/03 17:57:31]

Is there not a N:1 relationship between CompositorProxy and elementId?  As an
element can be involved in multiple CompositorWorker animations, creating a
CompositorProxy for it in each animation?

[flackr, 2017/04/11 17:51:36]

At least there is in the current implementation where you can create many
CompositorProxy objects for a single element. Acknowledged.

   const uint32_t m_compositorMutableProperties = 0;
 
   bool m_connected = true;
   CrossThreadPersistent<CompositorProxyClient> m_client;
   std::unique_ptr<CompositorMutableState> m_state;
 };
 
 }  // namespace blink
 
 #endif  // CompositorProxy_h