Log force-alt-protocols command line flag usage.

BUG=452514

Review URL: https://codereview.chromium.org/879863004

Cr-Commit-Position: refs/heads/master@{#313566}

chrome/browser/io_thread.cc

@@ -14,6 +14,7 @@
 #include "base/debug/leak_tracker.h"
 #include "base/logging.h"
 #include "base/metrics/field_trial.h"
+#include "base/metrics/user_metrics.h"
 #include "base/prefs/pref_registry_simple.h"
 #include "base/prefs/pref_service.h"
 #include "base/stl_util.h"
@@ -909,6 +910,7 @@ void IOThread::EnableSpdy(const std::string& mode) {
       globals_->use_alternate_protocols.set(false);
     } else if (option == kForceAltProtocols) {
       net::AlternateProtocolInfo pair(443, net::NPN_SPDY_3, 1);
+      base::RecordAction(base::UserMetricsAction("Net.ForceAlternateProtocol"));
       net::HttpServerPropertiesImpl::ForceAlternateProtocol(pair);
     } else if (option == kSingleDomain) {
       DVLOG(1) << "FORCING SINGLE DOMAIN";

tools/metrics/actions/actions.xml

@@ -8038,6 +8038,13 @@ should be able to be added at any place in this file.
   <description>Please enter the description of this user action.</description>
 </action>
 
+<action name="Net.ForceAlternateProtocol">
+  <owner>bnc@chromium.org</owner>
+  <description>
+    User forces alternate protocol via command line flag.
+  </description>
+</action>
+
 <action name="Net.URLRequest_StartJob_InvalidReferrer">
   <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
   <description>Please enter the description of this user action.</description>