Add ScheduleVerifier.

src/compiler/verifier.h

Index: src/compiler/verifier.h
diff --git a/src/compiler/verifier.h b/src/compiler/verifier.h
index 788c6a56579ddba2a485f46069f896b45ad401bc..b5c028ef30588c11db797a00be137c50942e89c3 100644
--- a/src/compiler/verifier.h
+++ b/src/compiler/verifier.h
@@ -7,12 +7,15 @@
 
 #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);
@@ -21,6 +24,12 @@ class Verifier {
   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