cc: Add id->LayerImpl map to LayerTreeImpl

cc/layer_tree_impl.h

Index: cc/layer_tree_impl.h
diff --git a/cc/layer_tree_impl.h b/cc/layer_tree_impl.h
index 6fc4429d9e7752d147f65e639df66901b49a758c..62e01354f5530c084edfa56935937613c834b9bc 100644
--- a/cc/layer_tree_impl.h
+++ b/cc/layer_tree_impl.h
@@ -5,8 +5,20 @@
 #ifndef CC_LAYER_TREE_IMPL_H_
 #define CC_LAYER_TREE_IMPL_H_
 
+#include "base/hash_tables.h"
 #include "cc/layer_impl.h"
 
+#if defined(COMPILER_GCC)

[danakj, 2012/12/13 23:57:11]

I would expect you to need an MSVC version too. If you do, see cc/hash_pair.h

[enne (OOO), 2012/12/14 00:21:12]

Nope.  That's just for std::pair being weird.  See layer_sorter.h or
layer_tree_host.h

+namespace BASE_HASH_NAMESPACE {
+template<>
+struct hash<cc::LayerImpl*> {
+  size_t operator()(cc::LayerImpl* ptr) const {
+    return hash<size_t>()(reinterpret_cast<size_t>(ptr));
+  }
+};
+} // namespace BASE_HASH_NAMESPACE
+#endif // COMPILER
+
 namespace cc {
 
 class DebugRectHistory;
@@ -70,6 +82,12 @@ class CC_EXPORT LayerTreeImpl {
 
   void ClearCurrentlyScrollingLayer();
 
+  LayerImpl* LayerById(int id);
+
+  // These should be called by LayerImpl's ctor/dtor.
+  void RegisterLayer(LayerImpl* layer);
+  void UnregisterLayer(LayerImpl* layer);
+
 protected:
   LayerTreeImpl(LayerTreeHostImpl* layer_tree_host_impl);
 
@@ -80,6 +98,9 @@ protected:
   LayerImpl* root_scroll_layer_;
   LayerImpl* currently_scrolling_layer_;
 
+  typedef base::hash_map<int, LayerImpl*> LayerIdMap;
+  LayerIdMap layer_id_map_;
+
   // Persisted state
   int scrolling_layer_id_from_previous_tree_;