Create histograms to track time-to-error values for different errors.

content/browser/loader/resource_dispatcher_host_impl.cc

Index: content/browser/loader/resource_dispatcher_host_impl.cc
diff --git a/content/browser/loader/resource_dispatcher_host_impl.cc b/content/browser/loader/resource_dispatcher_host_impl.cc
index d758f687987af444c94f1ed25d29cfbd25fc31d5..caa02ef8e34b75650a3e95366cb8e689e0850f8d 100644
--- a/content/browser/loader/resource_dispatcher_host_impl.cc
+++ b/content/browser/loader/resource_dispatcher_host_impl.cc
@@ -24,6 +24,7 @@
 #include "base/profiler/scoped_tracker.h"
 #include "base/stl_util.h"
 #include "base/third_party/dynamic_annotations/dynamic_annotations.h"
+#include "base/time/time.h"
 #include "content/browser/appcache/appcache_interceptor.h"
 #include "content/browser/appcache/chrome_appcache_service.h"
 #include "content/browser/cert_store_impl.h"
@@ -862,6 +863,41 @@ void ResourceDispatcherHostImpl::DidFinishLoading(ResourceLoader* loader) {
         "Net.ErrorCodesForMainFrame3",
         -loader->request()->status().error());
 
+    // Record time to success and error for the most common errors, and for
+    // the aggregate remainder errors.
+    base::TimeDelta request_loading_time(
+        base::Time::Now() - loader->request()->request_time());
+    switch (loader->request()->status().error()) {
+      case net::OK:
+        UMA_HISTOGRAM_LONG_TIMES(
+            "Net.RequestTime.Success", request_loading_time);
+        break;
+      case net::ERR_ABORTED:
+        UMA_HISTOGRAM_LONG_TIMES(
+            "Net.RequestTime.ErrAborted", request_loading_time);
+        break;
+      case net::ERR_CONNECTION_RESET:
+        UMA_HISTOGRAM_LONG_TIMES(
+            "Net.RequestTime.ErrConnectionReset", request_loading_time);
+        break;
+      case net::ERR_INTERNET_DISCONNECTED:
+        UMA_HISTOGRAM_LONG_TIMES(
+            "Net.RequestTime.ErrInternetDisconnected", request_loading_time);
+        break;
+      case net::ERR_NAME_NOT_RESOLVED:
+        UMA_HISTOGRAM_LONG_TIMES(
+            "Net.RequestTime.ErrNameNotResolved", request_loading_time);
+        break;
+      case net::ERR_TIMED_OUT:

[mmenke, 2015/05/12 20:57:00]

Josh was right about ERR_CONNECTION_TIMED_OUT - TIMED_OUT is pretty uncommon.  I
think we only get it on TCP keep-alive timeouts.  ERR_CONNECTION_TIMED_OUT is
when it takes too long to establish a connection, and is pretty clearly what you
want here.

[mmenke, 2015/05/12 20:58:15]

Oh, we also get it when we sent a TCP packet and never get a response, I guess.

+        UMA_HISTOGRAM_LONG_TIMES(
+            "Net.RequestTime.ErrTimedOut", request_loading_time);
+        break;
+      default:
+        UMA_HISTOGRAM_LONG_TIMES(
+            "Net.RequestTime.MiscError", request_loading_time);
+        break;
+    }
+
     if (loader->request()->url().SchemeIsCryptographic()) {
       if (loader->request()->url().host() == "www.google.com") {
         UMA_HISTOGRAM_SPARSE_SLOWLY("Net.ErrorCodesForHTTPSGoogleMainFrame2",