Switch cc to std::unordered_*.

cc/trees/layer_tree_host.cc

Index: cc/trees/layer_tree_host.cc
diff --git a/cc/trees/layer_tree_host.cc b/cc/trees/layer_tree_host.cc
index e2a736bcd6beb3fe8b59a8ba986131e72739ab4a..bff00c01a1259b218a200c8f2cbf8d8de2769135 100644
--- a/cc/trees/layer_tree_host.cc
+++ b/cc/trees/layer_tree_host.cc
@@ -10,6 +10,7 @@
 #include <algorithm>
 #include <stack>
 #include <string>
+#include <unordered_map>
 
 #include "base/atomic_sequence_num.h"
 #include "base/auto_reset.h"
@@ -64,7 +65,7 @@ namespace {
 
 Layer* UpdateAndGetLayer(Layer* current_layer,
                          int layer_id,
-                         const base::hash_map<int, Layer*>& layer_id_map) {
+                         const std::unordered_map<int, Layer*>& layer_id_map) {
   if (layer_id == Layer::INVALID_ID) {
     if (current_layer)
       current_layer->SetLayerTreeHost(nullptr);