Added integration test to Chrome Proxy to verify direct connection on remote site timeout

tools/chrome_proxy/testserver/server.go

Index: tools/chrome_proxy/testserver/server.go
diff --git a/tools/chrome_proxy/testserver/server.go b/tools/chrome_proxy/testserver/server.go
index 698e45ce46d1c3cfc1e997ef4a4a604db4509729..b8d9bf33a760406855ec2f4f9f8bd9eae8dfa802 100644
--- a/tools/chrome_proxy/testserver/server.go
+++ b/tools/chrome_proxy/testserver/server.go
@@ -35,12 +35,15 @@ import (
 	"net/http"
 	"os"
 	"strconv"
+	"strings"
+	"time"
 )
 
 func init() {
 	http.HandleFunc("/requestHeader", requestHeader)
 	http.HandleFunc("/resource", resource)
 	http.HandleFunc("/default", defaultResponse)
+	http.HandleFunc("/blackhole", blackholeProxy)
 }
 
 // requestHander returns request headers in response body as text.
@@ -82,6 +85,19 @@ func defaultResponse(w http.ResponseWriter, r *http.Request) {
 	}
 }
 
+// blackholePoxy delays longer than 90s test failure threshold to any request
+// coming from the proxy. Responds immediately to any other request.
+func blackholeProxy(w http.ResponseWriter, r *http.Request) {
+	if strings.Contains(r.Header.Get("via"), "Chrome-Compression-Proxy") {
+		// Causes timeout on proxy, will then send BLOCK_ONCE.
+		// Appspot will 502 traffic at 120 seconds with no response.

[sclittle, 2016/08/09 22:30:36]

115 seconds seems pretty close to 120 seconds - perhaps 100 or 90 seconds would
be less prone to flake?

[Robert Ogden, 2016/08/09 22:44:54]

Done.

+		time.Sleep(115 * time.Second);

[sclittle, 2016/08/09 22:30:36]

AIUI it's probably better to make the doc.ready timeout in the test considerably
longer than this delay here at the origin server, since then it's possible for
the test to actually get the "You are proxy" response if the proxy doesn't
timeout soon enough. That response would have the via header, and the test
checks that the response doesn't have the via header, so that would cause the
test to fail.

That way, the delay here at the origin server is the real deadline, and the
document.ready timeout in the test is just to prevent the test from running
forever.

Otherwise it isn't as clear if a test failure due to the 90s timeout was
triggered by flakiness or a bug in the proxy.

[Robert Ogden, 2016/08/09 22:44:54]

Ah, that's a good point. I like that logic

+		w.Write([]byte("You are proxy"));
+	} else {
+		w.Write([]byte("You are direct"));
+	}
+}
+
 type override struct {
 	status int
 	header http.Header