Introduce Dart_SetVMFlags API function.

runtime/vm/flags.cc

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/flags.h"
 
 #include "vm/assert.h"
 #include "vm/os.h"
 
 namespace dart {
 
 DEFINE_FLAG(bool, print_flags, false, "Print flags as they are being parsed.");
 DEFINE_FLAG(bool, ignore_unrecognized_flags, false,
     "Ignore unrecognized flags.");
 
 // List of registered flags.
 Flag* Flags::flags_ = NULL;
 
+bool Flags::initialized_ = false;
+
 class Flag {
  public:
   enum Type {
     kBoolean,
     kInteger,
     kString,
     kNumFlagTypes
   };
 
   Flag(const char* name, const char* comment, void* addr, Type type)
@@ skipping 189 matching lines @@
 
 static bool IsValidFlag(const char* name,
                         const char* prefix,
                         intptr_t prefix_length) {
   intptr_t name_length = strlen(name);
   return ((name_length > prefix_length) &&
           (strncmp(name, prefix, prefix_length) == 0));
 }
 
 
-void Flags::ProcessCommandLineFlags(int number_of_vm_flags,
+bool Flags::ProcessCommandLineFlags(int number_of_vm_flags,
                                     const char** vm_flags) {
+  if (initialized_) {
+    return false;
+  }
+
+  initialized_ = true;
+
   const char* kPrefix = "--";
   const intptr_t kPrefixLen = strlen(kPrefix);
 
   int i = 0;
   while ((i < number_of_vm_flags) &&
          IsValidFlag(vm_flags[i], kPrefix, kPrefixLen)) {
     const char* option = vm_flags[i] + kPrefixLen;
     Parse(option);
     i++;
   }
@@ skipping 18 matching lines @@
     }
   }
   if (FLAG_print_flags) {
     OS::Print("Flag settings:\n");
     Flag* flag = Flags::flags_;
     while (flag != NULL) {
       flag->Print();
       flag = flag->next_;
     }
   }
+
+  return true;
 }
 
 }  // namespace dart