Send all field trials from the browser.

chrome/renderer/chrome_render_process_observer.cc

Index: chrome/renderer/chrome_render_process_observer.cc
diff --git a/chrome/renderer/chrome_render_process_observer.cc b/chrome/renderer/chrome_render_process_observer.cc
index 2e8d4ee943222e3cdde1413f7337a536e2eb30a5..860dd326207efef5a7acdff9ab69120b9d48e066 100644
--- a/chrome/renderer/chrome_render_process_observer.cc
+++ b/chrome/renderer/chrome_render_process_observer.cc
@@ -305,6 +305,8 @@ ChromeRenderProcessObserver::ChromeRenderProcessObserver(
 #endif
   // Setup initial set of crash dump data for Field Trials in this renderer.
   chrome_variations::SetChildProcessLoggingVariationList();
+  // Listen for field trial activations to report them to the browser.
+  base::FieldTrialList::AddObserver(this);
 }
 
 ChromeRenderProcessObserver::~ChromeRenderProcessObserver() {
@@ -371,8 +373,8 @@ void ChromeRenderProcessObserver::OnSetFieldTrialGroup(
       base::FieldTrialList::CreateFieldTrial(field_trial_name, group_name);
   // TODO(mef): Remove this check after the investigation of 359406 is complete.
   CHECK(trial) << field_trial_name << ":" << group_name;
-  // Ensure the trial is marked as "used" by calling group() on it. This is
-  // needed to ensure the trial is properly reported in renderer crash reports.
+  // Ensure the trial is marked as "used" by calling group() on it if it is
+  // marked as activated.
   trial->group();
   chrome_variations::SetChildProcessLoggingVariationList();
 }
@@ -385,3 +387,10 @@ const RendererContentSettingRules*
 ChromeRenderProcessObserver::content_setting_rules() const {
   return &content_setting_rules_;
 }
+
+void ChromeRenderProcessObserver::OnFieldTrialGroupFinalized(
+    const std::string& trial_name,
+    const std::string& group_name) {
+  content::RenderThread::Get()->Send(
+      new ChromeViewHostMsg_FieldTrialActivated(trial_name));
+}