Deprecte LoweringBuilder in favor of Reducer.

src/compiler/js-generic-lowering.cc

Index: src/compiler/js-generic-lowering.cc
diff --git a/src/compiler/js-generic-lowering.cc b/src/compiler/js-generic-lowering.cc
index 68cc1cea9053358bbd5a065647e8300b83bdc56e..e7dbd8020c900924f418f4fdc0a863c5e5e1795c 100644
--- a/src/compiler/js-generic-lowering.cc
+++ b/src/compiler/js-generic-lowering.cc
@@ -156,10 +156,8 @@ class KeyedStoreICStubShim : public HydrogenCodeStub {
 
 
 JSGenericLowering::JSGenericLowering(CompilationInfo* info, JSGraph* jsgraph,
-                                     MachineOperatorBuilder* machine,
-                                     SourcePositionTable* source_positions)
-    : LoweringBuilder(jsgraph->graph(), source_positions),
-      info_(info),
+                                     MachineOperatorBuilder* machine)
+    : info_(info),
       jsgraph_(jsgraph),
       linkage_(new (jsgraph->zone()) Linkage(info)),
       machine_(machine) {}
@@ -200,7 +198,7 @@ Node* JSGenericLowering::ExternalConstant(ExternalReference ref) {
 }
 
 
-void JSGenericLowering::Lower(Node* node) {
+Reduction JSGenericLowering::Reduce(Node* node) {
   Node* replacement = NULL;
   // Dispatch according to the opcode.
   switch (node->opcode()) {
@@ -213,14 +211,10 @@ void JSGenericLowering::Lower(Node* node) {
 #undef DECLARE_CASE
     default:
       // Nothing to see.
-      return;
+      return NoChange();
   }
-
-  // Nothing to do if lowering was done by patching the existing node.
-  if (replacement == node) return;
-
-  // Iterate through uses of the original node and replace uses accordingly.
-  UNIMPLEMENTED();
+  DCHECK_EQ(node, replacement);
+  return Changed(replacement);
 }