Avoid exposing cc::Layer tree to CompositorProxy

third_party/WebKit/Source/core/dom/CompositorProxy.cpp

Index: third_party/WebKit/Source/core/dom/CompositorProxy.cpp
diff --git a/third_party/WebKit/Source/core/dom/CompositorProxy.cpp b/third_party/WebKit/Source/core/dom/CompositorProxy.cpp
index e715638b804f420fddba14fb52c421ec4cc444a1..de1b0280d46a1866abf7ba4d7aeb4ad2cff75851 100644
--- a/third_party/WebKit/Source/core/dom/CompositorProxy.cpp
+++ b/third_party/WebKit/Source/core/dom/CompositorProxy.cpp
@@ -19,6 +19,11 @@
 #include <algorithm>
 
 namespace blink {
+namespace {
+// An identifier for CompositorProxy objects. Will be unique across all proxies
+// created in the same thread.
+uint64_t uniqueId = 0;
+}  // namespace
 
 static const struct {
   const char* name;
@@ -135,6 +140,7 @@ CompositorProxy* CompositorProxy::create(ExecutionContext* context,
 CompositorProxy::CompositorProxy(uint64_t elementId,
                                  uint32_t compositorMutableProperties)
     : m_elementId(elementId),
+      m_proxyId(uniqueId++),
       m_compositorMutableProperties(compositorMutableProperties),
       m_client(nullptr) {
   DCHECK(m_compositorMutableProperties);