Android: register synthetic field trials correctly.

The previous registration in SetupMobileFieldTrials was too early;
the g_browser_process is not initialized yet. This registration works.

Bug: 932578
Change-Id: If45b6b88c1be4c1025f9ecd6ee8e5efc5685bc9d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1473174Reviewed-by: David Roger <droger@chromium.org>
Reviewed-by: Alexei Svitkine <asvitkine@chromium.org>
Reviewed-by: François Doray <fdoray@chromium.org>
Commit-Queue: Matthew Cary <mattcary@chromium.org>
Auto-Submit: Matthew Cary <mattcary@chromium.org>
Cr-Commit-Position: refs/heads/master@{#638075}

chrome/browser/chrome_browser_field_trials.cc

@@ -13,6 +13,7 @@
 #include "base/strings/string_util.h"
 #include "base/time/time.h"
 #include "build/build_config.h"
+#include "chrome/browser/metrics/chrome_metrics_service_accessor.h"
 #include "chrome/browser/metrics/chrome_metrics_service_client.h"
 #include "chrome/browser/metrics/chrome_metrics_services_manager_client.h"
 #include "chrome/browser/metrics/persistent_histograms.h"
@@ -23,6 +24,8 @@
 #include "components/version_info/version_info.h"
 
 #if defined(OS_ANDROID)
+#include "base/android/library_loader/library_loader_hooks.h"
+#include "base/android/reached_code_profiler.h"
 #include "chrome/browser/chrome_browser_field_trials_mobile.h"
 #else
 #include "chrome/browser/chrome_browser_field_trials_desktop.h"
@@ -85,6 +88,33 @@ void ChromeBrowserFieldTrials::SetupFeatureControllingFieldTrials(
   }
 }
 
+void ChromeBrowserFieldTrials::RegisterSyntheticTrials() {
+#if defined(OS_ANDROID)
+  static constexpr char kEnabledGroup[] = "Enabled";
+  static constexpr char kDisabledGroup[] = "Disabled";
+
+  static constexpr char kOrderfileOptimizationTrial[] =
+      "AndroidOrderfileOptimization";
+  if (base::android::IsUsingOrderfileOptimization()) {
+    ChromeMetricsServiceAccessor::RegisterSyntheticFieldTrial(
+        kOrderfileOptimizationTrial, kEnabledGroup);
+  } else {
+    ChromeMetricsServiceAccessor::RegisterSyntheticFieldTrial(
+        kOrderfileOptimizationTrial, kDisabledGroup);
+  }
+
+  static constexpr char kReachedCodeProfilerTrial[] =
+      "ReachedCodeProfilerSynthetic";
+  if (base::android::IsReachedCodeProfilerEnabled()) {
+    ChromeMetricsServiceAccessor::RegisterSyntheticFieldTrial(
+        kReachedCodeProfilerTrial, kEnabledGroup);
+  } else {
+    ChromeMetricsServiceAccessor::RegisterSyntheticFieldTrial(
+        kReachedCodeProfilerTrial, kDisabledGroup);
+  }
+#endif  // defined(OS_ANDROID)
+}
+
 void ChromeBrowserFieldTrials::InstantiateDynamicTrials() {
   // Persistent histograms must be enabled as soon as possible.
   InstantiatePersistentHistograms();

chrome/browser/chrome_browser_field_trials.h

@@ -22,6 +22,7 @@ class ChromeBrowserFieldTrials : public variations::PlatformFieldTrials {
   void SetupFeatureControllingFieldTrials(
       bool has_seed,
       base::FeatureList* feature_list) override;
+  void RegisterSyntheticTrials() override;
 
  private:
   // Instantiates dynamic trials by querying their state, to ensure they get

chrome/browser/chrome_browser_field_trials_mobile.cc

@@ -5,48 +5,18 @@
 #include "chrome/browser/chrome_browser_field_trials_mobile.h"
 
 #include "build/build_config.h"
+#include "chrome/browser/browser_process.h"
 
 #if defined(OS_ANDROID)
-#include "base/android/library_loader/library_loader_hooks.h"
-#include "base/android/reached_code_profiler.h"
-#include "base/base_switches.h"
-#include "chrome/browser/browser_process.h"
-#include "chrome/browser/metrics/chrome_metrics_service_accessor.h"
 #include "chrome/browser/prerender/prerender_field_trial.h"
 #endif
 
 namespace chrome {
 
 void SetupMobileFieldTrials() {
+  DCHECK(!g_browser_process);
 #if defined(OS_ANDROID)
   prerender::ConfigureNoStatePrefetch();
-
-  // For tests on some platforms, g_browser_process is not initialized yet.
-  if (g_browser_process) {
-    static constexpr char kEnabledGroup[] = "Enabled";
-    static constexpr char kDisabledGroup[] = "Disabled";
-
-    static constexpr char kOrderfileOptimizationTrial[] =
-        "AndroidOrderfileOptimization";
-    if (base::android::IsUsingOrderfileOptimization()) {
-      ChromeMetricsServiceAccessor::RegisterSyntheticFieldTrial(
-          kOrderfileOptimizationTrial, kEnabledGroup);
-    } else {
-      ChromeMetricsServiceAccessor::RegisterSyntheticFieldTrial(
-          kOrderfileOptimizationTrial, kDisabledGroup);
-    }
-
-    static constexpr char kReachedCodeProfilerTrial[] =
-        "ReachedCodeProfilerSynthetic";
-    if (base::android::IsReachedCodeProfilerEnabled()) {
-      ChromeMetricsServiceAccessor::RegisterSyntheticFieldTrial(
-          kReachedCodeProfilerTrial, kEnabledGroup);
-    } else {
-      ChromeMetricsServiceAccessor::RegisterSyntheticFieldTrial(
-          kReachedCodeProfilerTrial, kDisabledGroup);
-    }
-  }
-
 #endif
 }
 

chrome/browser/chrome_browser_main.cc

@@ -661,6 +661,9 @@ void ChromeBrowserMainParts::SetupMetrics() {
       variations::SyntheticTrialsActiveGroupIdProvider::GetInstance());
   // Now that field trials have been created, initializes metrics recording.
   metrics->InitializeMetricsRecordingState();
+
+  chrome_feature_list_creator_->browser_field_trials()
+      ->RegisterSyntheticTrials();
 }
 
 void ChromeBrowserMainParts::StartMetricsRecording() {

chrome/browser/chrome_browser_main.h

@@ -10,7 +10,6 @@
 
 #include "base/macros.h"
 #include "build/build_config.h"
-#include "chrome/browser/chrome_browser_field_trials.h"
 #include "chrome/browser/chrome_process_singleton.h"
 #include "chrome/browser/first_run/first_run.h"
 #include "chrome/browser/process_singleton.h"
@@ -138,8 +137,6 @@ class ChromeBrowserMainParts : public content::BrowserMainParts {
   const base::CommandLine& parsed_command_line_;
   int result_code_;
 
-  ChromeBrowserFieldTrials browser_field_trials_;
-
 #if !defined(OS_ANDROID)
   // Create StartupTimeBomb object for watching jank during startup.
   std::unique_ptr<StartupTimeBomb> startup_watcher_;

chrome/browser/metrics/chrome_feature_list_creator.h

@@ -69,6 +69,10 @@ class ChromeFeatureListCreator {
   }
   const std::string& actual_locale() { return actual_locale_; }
 
+  ChromeBrowserFieldTrials* browser_field_trials() {
+    return browser_field_trials_.get();
+  }
+
  private:
   void CreatePrefService();
   void ConvertFlagsToSwitches();

chrome/browser/metrics/chrome_metrics_service_accessor.h

@@ -85,7 +85,7 @@ class ChromeMetricsServiceAccessor : public metrics::MetricsServiceAccessor {
   friend class ::CrashesDOMHandler;
   friend class ::FlashDOMHandler;
   friend void chrome::AttemptRestart();
-  friend void chrome::SetupMobileFieldTrials();
+  friend class ChromeBrowserFieldTrials;
   // For ChromeWinClang.
   friend class ChromeBrowserMainExtraPartsMetrics;
   // For StackSamplingConfiguration.

components/variations/platform_field_trials.h

@@ -29,6 +29,10 @@ class PlatformFieldTrials {
       bool has_seed,
       base::FeatureList* feature_list) = 0;
 
+  // Register any synthetic field trials. Will be called later than the above
+  // methods, in particular after g_browser_process is available..
+  virtual void RegisterSyntheticTrials() {}
+
  private:
   DISALLOW_COPY_AND_ASSIGN(PlatformFieldTrials);
 };