Add field trial for A/B testing of SSL False Start.

chrome/renderer/page_load_histograms.cc

Index: chrome/renderer/page_load_histograms.cc
===================================================================
--- chrome/renderer/page_load_histograms.cc	(revision 75321)
+++ chrome/renderer/page_load_histograms.cc	(working copy)
@@ -796,6 +796,27 @@
     }
   }
 
+  static bool false_start_trial(base::FieldTrialList::Find("SSLFalseStart") &&
+      !base::FieldTrialList::Find("SSLFalseStart")->group_name().empty());
+  if (false_start_trial) {
+    if (scheme_type == URLPattern::SCHEME_HTTPS) {
+      switch (load_type) {
+        case NavigationState::LINK_LOAD_NORMAL:
+          PLT_HISTOGRAM(base::FieldTrial::MakeName(
+              "PLT.BeginToFinish_LinkLoadNormal", "SSLFalseStart"),
+              begin_to_finish_all_loads);
+          break;
+        case NavigationState::NORMAL_LOAD:
+          PLT_HISTOGRAM(base::FieldTrial::MakeName(
+              "PLT.BeginToFinish_NormalLoad", "SSLFalseStart"),
+              begin_to_finish_all_loads);
+          break;
+        default:
+          break;
+      }
+    }
+  }
+
   // Site isolation metrics.
   UMA_HISTOGRAM_COUNTS("SiteIsolation.PageLoadsWithCrossSiteFrameAccess",
                        cross_origin_access_count_);