Mock the LinkDoctor for tests. Should greatly decrease ErrorPage test flakiness.

chrome/browser/google_util.cc

Index: chrome/browser/google_util.cc
diff --git a/chrome/browser/google_util.cc b/chrome/browser/google_util.cc
index 0949d2f072b82d475daaecbac4c27aafe8fcdb2e..9cb5e229228ccc2ea04117c0a771527d0c5a9828 100644
--- a/chrome/browser/google_util.cc
+++ b/chrome/browser/google_util.cc
@@ -31,6 +31,9 @@ GURL AppendParam(const GURL& url,
 
 namespace google_util {
 
+const char kLinkDoctorBaseURL[] =
+    "http://linkhelp.clients.google.com/tbproxy/lh/fixurl";
+
 GURL AppendGoogleLocaleParam(const GURL& url) {
   return AppendParam(url, "hl",
                      g_browser_process->GetApplicationLocale());