Improve performance of proxy resolver by tracing DNS dependencies.

net/net_unittests.isolate

Index: net/net_unittests.isolate
diff --git a/net/net_unittests.isolate b/net/net_unittests.isolate
index b3c8d7b354c59166d5fa398a08afbba603caf378..fe7dbf3bca0720997eacbd8353741f1bd6b36118 100644
--- a/net/net_unittests.isolate
+++ b/net/net_unittests.isolate
@@ -228,6 +228,13 @@
     }, {
       'variables': {
         'isolate_dependency_tracked': [
+          'data/proxy_resolver_v8_tracing_unittest/dns_during_init.js',
+          'data/proxy_resolver_v8_tracing_unittest/dns.js',
+          'data/proxy_resolver_v8_tracing_unittest/error.js',
+          'data/proxy_resolver_v8_tracing_unittest/global_sideffects1.js',
+          'data/proxy_resolver_v8_tracing_unittest/global_sideffects2.js',
+          'data/proxy_resolver_v8_tracing_unittest/simple.js',
+          'data/proxy_resolver_v8_tracing_unittest/too_many_alerts.js',
           'data/proxy_resolver_v8_unittest/binding_from_global.js',
           'data/proxy_resolver_v8_unittest/bindings.js',
           'data/proxy_resolver_v8_unittest/direct.js',