Fix build

runtime/vm/service.cc

 // Copyright (c) 2013, 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/service.h"
 
 #include "include/dart_api.h"
 #include "platform/globals.h"
 
 #include "vm/compiler.h"
@@ skipping 1155 matching lines @@
   JSONObject jsobj(js);
   jsobj.AddProperty("type", "Sentinel");
   jsobj.AddProperty("id", id);
   jsobj.AddProperty("valueAsString", preview);
 }
 
 
 static SourceBreakpoint* LookupBreakpoint(Isolate* isolate, const char* id) {
   size_t end_pos = strcspn(id, "/");
   if (end_pos == strlen(id)) {
-    return false;
+    return NULL;
   }
   const char* rest = id + end_pos + 1;  // +1 for '/'.
   if (strncmp("breakpoints", id, end_pos) == 0) {
     intptr_t bpt_id = 0;
     SourceBreakpoint* bpt = NULL;
     if (GetIntegerId(rest, &bpt_id)) {
       bpt = isolate->debugger()->GetBreakpointById(bpt_id);
     }
     return bpt;
   }
@@ skipping 1439 matching lines @@
     ServiceMethodDescriptor& method = service_methods_[i];
     if (strcmp(method_name, method.name) == 0) {
       return &method;
     }
   }
   return NULL;
 }
 
 
 }  // namespace dart