Improve performance of proxy resolver by tracing DNS dependencies.

net/data/proxy_resolver_v8_tracing_unittest/global_sideffects1.js

Index: net/data/proxy_resolver_v8_tracing_unittest/global_sideffects1.js
diff --git a/net/data/proxy_resolver_v8_tracing_unittest/global_sideffects1.js b/net/data/proxy_resolver_v8_tracing_unittest/global_sideffects1.js
new file mode 100644
index 0000000000000000000000000000000000000000..251af9f754621ddec247f294908015f062cd88c6
--- /dev/null
+++ b/net/data/proxy_resolver_v8_tracing_unittest/global_sideffects1.js
@@ -0,0 +1,14 @@
+var g_iteration = 0;
+
+function FindProxyForURL(url, host) {
+  g_iteration++;
+
+  var ips = [
+    dnsResolve('host1'),
+    dnsResolve('crazy' + g_iteration)
+  ];
+
+  alert('iteration: ' + g_iteration);
+
+  return 'PROXY ' + ips.join('-') + ':100';
+}