[wasm] Debug-time print for compiler graph

Simple "Print" API for the compiler graph.

BUG=

Review-Url: https://codereview.chromium.org/2447993002
Cr-Commit-Position: refs/heads/master@{#40571}

src/compiler/graph.cc

@@ -7,8 +7,9 @@
 #include <algorithm>
 
 #include "src/base/bits.h"
-#include "src/compiler/node.h"
+#include "src/compiler/graph-visualizer.h"
 #include "src/compiler/node-properties.h"
+#include "src/compiler/node.h"
 #include "src/compiler/verifier.h"
 
 namespace v8 {
@@ -72,6 +73,11 @@ NodeId Graph::NextNodeId() {
   return id;
 }
 
+void Graph::Print() const {
+  OFStream os(stdout);
+  os << AsRPO(*this);
+}
+
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8

src/compiler/graph.h

@@ -121,6 +121,9 @@ class V8_EXPORT_PRIVATE Graph final : public NON_EXPORTED_BASE(ZoneObject) {
   void AddDecorator(GraphDecorator* decorator);
   void RemoveDecorator(GraphDecorator* decorator);
 
+  // Very simple print API usable in a debugger.
+  void Print() const;
+
  private:
   friend class NodeMarkerBase;