Add ScheduleVerifier.

src/compiler/verifier.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_VERIFIER_H_
 #define V8_COMPILER_VERIFIER_H_
 
 #include "src/v8.h"
 
-#include "src/compiler/graph.h"
-
 namespace v8 {
 namespace internal {
 namespace compiler {
 
+class Graph;
+class Schedule;
+
+// Verifies properties of a graph, such as the well-formedness of inputs to
+// each node, etc.
 class Verifier {
  public:
   static void Run(Graph* graph);
 
  private:
   class Visitor;
   DISALLOW_COPY_AND_ASSIGN(Verifier);
 };
+
+// Verifies properties of a schedule, such as dominance, phi placement, etc.
+class ScheduleVerifier {
+ public:
+  static void Run(Schedule* schedule);
+};
 }
 }
 }  // namespace v8::internal::compiler
 
 #endif  // V8_COMPILER_VERIFIER_H_