Implement graph trimming in ControlReducer.

src/compiler/control-reducer.h

+// Copyright 2014 the V8 project 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 V8_COMPILER_CONTROL_REDUCER_H_
+#define V8_COMPILER_CONTROL_REDUCER_H_
+
+namespace v8 {
+namespace internal {
+namespace compiler {
+
+class JSGraph;
+class CommonOperatorBuilder;
+
+class ControlReducer {
+ public:
+  // Perform branch folding and dead code elimination on the graph.
+  static void ReduceGraph(JSGraph* graph, CommonOperatorBuilder* builder);
+
+  // Trim nodes in the graph that are not reachable from end.
+  static void TrimGraph(JSGraph* graph);
+};
+}
+}
+}  // namespace v8::internal::compiler
+
+#endif  // V8_COMPILER_CONTROL_REDUCER_H_