Add ProxyResolverFactoryV8Tracing.

net/data/proxy_resolver_v8_tracing_unittest/error_on_load.js

Index: net/data/proxy_resolver_v8_tracing_unittest/error_on_load.js
diff --git a/net/data/proxy_resolver_v8_tracing_unittest/error_on_load.js b/net/data/proxy_resolver_v8_tracing_unittest/error_on_load.js
new file mode 100644
index 0000000000000000000000000000000000000000..6dfe9942b6d04ec17019052a30a6b2169b1895af
--- /dev/null
+++ b/net/data/proxy_resolver_v8_tracing_unittest/error_on_load.js
@@ -0,0 +1,7 @@
+alert('Prepare to DIE!');

[eroman, 2015/05/05 00:04:55]

Note: You may hit some presubmit warning about lack of copyright (we have
something baked in that enforces it on all *.js). If you need to add a copyright
line don't worry about getting another review pass for it.

[Sam McNally, 2015/05/05 01:31:36]

Done. The presubmit's already unhappy about the extra ScopedAllowIO.

+var x = null;
+return x.split('-');  // Throws exception.
+
+function FindProxyForURL(url, host) {
+  return "PROXY i-approve-this-message:42";
+}