Fix generation of pprof output.

runtime/bin/main.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 <stdlib.h>
 #include <string.h>
 #include <stdio.h>
 
 #include "include/dart_api.h"
 
@@ skipping 25 matching lines @@
   const intptr_t length = strlen(name);
   if (strncmp(option, name, length) == 0) {
     return (option + length);
   }
   return NULL;
 }
 
 
 static bool ProcessPprofOption(const char* option) {
   const char* kProfOption = "--generate_pprof_symbols=";
-  generate_pprof_symbols_filename = ProcessOption(option, kProfOption);
-  return generate_pprof_symbols_filename != NULL;
+  const char* filename = ProcessOption(option, kProfOption);
+  if (filename != NULL) {
+    generate_pprof_symbols_filename = filename;
+  }
+  return filename != NULL;
 }
 
 
 // Parse out the command line arguments. Returns -1 if the arguments
 // are incorrect, 0 otherwise.
 static int ParseArguments(int argc,
                           char** argv,
                           CommandLineOptions* vm_options,
                           char** script_name,
                           CommandLineOptions* dart_options) {
   const char* kPrefix = "--";
   const intptr_t kPrefixLen = strlen(kPrefix);
 
   // Skip the binary name.
   int i = 1;
 
   // Parse out the vm options.
   while ((i < argc) && IsValidFlag(argv[i], kPrefix, kPrefixLen)) {
     if (ProcessPprofOption(argv[i])) {
       i += 1;
-      Dart_InitPprofSupport();
       continue;
     }
     vm_options->AddArgument(argv[i]);
     i += 1;
   }
+  if (generate_pprof_symbols_filename != NULL) {
+    Dart_InitPprofSupport();
+  }
 
   // Get the script name.
   if (i < argc) {
     *script_name = argv[i];
     i += 1;
   } else {
     return -1;
   }
 
   // Parse out options to be passed to dart main.
@@ skipping 229 matching lines @@
     return 255;  // Indicates we encountered an error.
   }
   free(canonical_script_name);
   Dart_ExitScope();
   // Dump symbol information for the profiler.
   DumpPprofSymbolInfo();
   // Shutdown the isolate.
   Dart_ShutdownIsolate();
   return 0;
 }