Add a version tag for cached data.

src/flags.cc

 // Copyright 2006-2008 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.
 
 #include <cctype>
 #include <cstdlib>
 #include <sstream>
 
 #include "src/v8.h"
 
 #include "src/assembler.h"
+#include "src/base/functional.h"
 #include "src/base/platform/platform.h"
 #include "src/ostreams.h"
 
 namespace v8 {
 namespace internal {
 
 // Define all of our flags.
 #define FLAG_MODE_DEFINE
 #include "src/flag-definitions.h"  // NOLINT
 
@@ skipping 520 matching lines @@
 }
 
 
 // static
 void FlagList::EnforceFlagImplications() {
 #define FLAG_MODE_DEFINE_IMPLICATIONS
 #include "src/flag-definitions.h"
 #undef FLAG_MODE_DEFINE_IMPLICATIONS
 }
 
+
+uint32_t FlagList::Hash() {
+  std::ostringstream modified_args_as_string;
+  for (size_t i = 0; i < num_flags; ++i) {
+    Flag* current = &flags[i];
+    if (!current->IsDefault()) {
+      modified_args_as_string << *current;
+    }
+  }
+  std::string args(modified_args_as_string.str());
+  return static_cast<uint32_t>(
+      base::hash_range(args.c_str(), args.c_str() + args.length()));
+}
 } }  // namespace v8::internal