Add a command line flag to change the default number of parallel DNS requests...

net/base/host_resolver_impl.cc

Index: net/base/host_resolver_impl.cc
===================================================================
--- net/base/host_resolver_impl.cc	(revision 52747)
+++ net/base/host_resolver_impl.cc	(working copy)
@@ -52,13 +52,17 @@
 
 }  // anonymous namespace
 
-HostResolver* CreateSystemHostResolver() {
+HostResolver* CreateSystemHostResolver(size_t max_concurrent_resolves) {
   // Maximum of 50 concurrent threads.
   // TODO(eroman): Adjust this, do some A/B experiments.
-  static const size_t kMaxJobs = 50u;
+  static const size_t kDefaultMaxJobs = 50u;
 
+  if (max_concurrent_resolves == HostResolver::kDefaultParallelism)
+    max_concurrent_resolves = kDefaultMaxJobs;
+
   HostResolverImpl* resolver =
-      new HostResolverImpl(NULL, CreateDefaultCache(), kMaxJobs);
+      new HostResolverImpl(NULL, CreateDefaultCache(),
+                           max_concurrent_resolves);
 
   return resolver;
 }