Removing Variations support for google_update_experiment_id.

chrome/browser/metrics/variations/chrome_variations_service_client.cc

Index: chrome/browser/metrics/variations/chrome_variations_service_client.cc
diff --git a/chrome/browser/metrics/variations/chrome_variations_service_client.cc b/chrome/browser/metrics/variations/chrome_variations_service_client.cc
index 72608016ec6f6efbe11f2143bc6248fa9584e880..3adb256d403243064869f4f6dc1137d86a46895c 100644
--- a/chrome/browser/metrics/variations/chrome_variations_service_client.cc
+++ b/chrome/browser/metrics/variations/chrome_variations_service_client.cc
@@ -11,6 +11,17 @@
 #include "components/version_info/version_info.h"
 #include "content/public/browser/browser_thread.h"
 
+#if defined(OS_WIN)
+#include "base/files/file_path.h"
+#include "base/metrics/histogram_macros.h"
+#include "base/path_service.h"
+#include "base/strings/string16.h"
+#include "base/threading/thread_restrictions.h"
+#include "chrome/installer/util/google_update_settings.h"
+#include "chrome/installer/util/install_util.h"
+#include "components/variations/experiment_labels.h"
+#endif
+
 #if !defined(OS_ANDROID) && !defined(OS_CHROMEOS)
 #include "chrome/browser/upgrade_detector_impl.h"
 #endif
@@ -36,6 +47,51 @@ base::Version GetVersionForSimulation() {
   return base::Version(version_info::GetVersionNumber());
 }
 
+#if defined(OS_WIN)
+// Clear all Variations experiment labels from Google Update Registry Labels.
+// TODO(jwd): Remove this once we're confident most clients no longer have these
+// labels (M57-M58 timeframe).
+void ClearGoogleUpdateRegistryLabels() {
+  base::ThreadRestrictions::AssertIOAllowed();
+
+  // Note that all registry operations are done here on the UI thread as there
+  // are no threading restrictions on them.
+  base::FilePath chrome_exe;
+  if (!PathService::Get(base::FILE_EXE, &chrome_exe)) {
+    NOTREACHED() << "Failed to get chrome exe path";
+    return;
+  }
+  const bool is_system_install = !InstallUtil::IsPerUserInstall(chrome_exe);
+
+  // Read the current bits from the registry.
+  base::string16 registry_labels;
+  bool success = GoogleUpdateSettings::ReadExperimentLabels(is_system_install,
+                                                            &registry_labels);
+
+  if (!success) {
+    DVLOG(1) << "Error reading Variation labels from the registry.";
+    return;
+  }
+
+  // Only keep the non-Variations contents of experiment_labels.
+  const base::string16 labels_to_keep =
+      variations::ExtractNonVariationLabels(registry_labels);
+
+  // This is a weak check, which can give false positives if the implementation
+  // of variations::ExtractNonVariationLabels changes, but should be fine for
+  // temporary code.
+  bool needs_clearing = labels_to_keep != registry_labels;
+
+  UMA_HISTOGRAM_BOOLEAN("Variations.GoogleUpdateRegistryLabelsNeedClearing",
+                        needs_clearing);
+
+  if (!needs_clearing)
+    return;
+
+  GoogleUpdateSettings::SetExperimentLabels(is_system_install, labels_to_keep);
+}
+#endif  // defined(OS_WIN)
+
 }  // namespace
 
 ChromeVariationsServiceClient::ChromeVariationsServiceClient() {}
@@ -82,12 +138,11 @@ bool ChromeVariationsServiceClient::OverridesRestrictParameter(
 
 void ChromeVariationsServiceClient::OnInitialStartup() {
 #if defined(OS_WIN)
-  StartGoogleUpdateRegistrySync();
+  // TODO(jwd): Remove this once we're confident most clients no longer have
+  // these labels (M57-M58 timeframe).
+  // Do the work on a blocking pool thread, as chrome://profiler has shown that
+  // it can cause jank if done on the UI thrread.
+  content::BrowserThread::GetBlockingPool()->PostTask(
+      FROM_HERE, base::Bind(&ClearGoogleUpdateRegistryLabels));

[Alexei Svitkine (slow), 2016/11/03 17:09:36]

Previously, it would be started with a delay. Can you keep the delay here?

[jwd, 2016/11/04 15:05:15]

Done.

 #endif
 }
-
-#if defined(OS_WIN)
-void ChromeVariationsServiceClient::StartGoogleUpdateRegistrySync() {
-  registry_syncer_.RequestRegistrySync();
-}
-#endif