Consolidates accessing and setting the UMA pref to be within metrics code

chrome/browser/metrics/metrics_reporting_state.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/metrics/metrics_reporting_state.h"
 
-#include "base/threading/thread_restrictions.h"
+#include "base/callback.h"
+#include "base/metrics/histogram.h"
+#include "base/prefs/pref_service.h"
 #include "chrome/browser/browser_process.h"
+#include "chrome/browser/metrics/chrome_metrics_service_accessor.h"
+#include "chrome/common/pref_names.h"
 #include "chrome/installer/util/google_update_settings.h"
 #include "components/metrics/metrics_service.h"
+#include "content/public/browser/browser_thread.h"
 
-bool ResolveMetricsReportingEnabled(bool enabled) {
-  // GoogleUpdateSettings touches the disk from the UI thread. MetricsService
-  // also calls GoogleUpdateSettings below. http://crbug/62626
-  base::ThreadRestrictions::ScopedAllowIO allow_io;
+namespace {
 
+enum MetricsReportingChangeHistogramValue {
+  METRICS_REPORTING_ERROR,
+  METRICS_REPORTING_DISABLED,
+  METRICS_REPORTING_ENABLED,
+  METRICS_REPORTING_MAX
+};
+
+void RecordMetricsReportingHistogramValue(
+    MetricsReportingChangeHistogramValue value) {
+  UMA_HISTOGRAM_ENUMERATION(
+      "UMA.MetricsReporting.Toggle", value, METRICS_REPORTING_MAX);
+}
+
+// Tries to set metrics reporting status to |enabled| and returns whatever is
+// the result of the update.
+bool SetGoogleUpdateSettings(bool enabled) {
   GoogleUpdateSettings::SetCollectStatsConsent(enabled);
-  bool update_pref = GoogleUpdateSettings::GetCollectStatsConsent();
+  bool updated_pref = GoogleUpdateSettings::GetCollectStatsConsent();
+  if (enabled != updated_pref)
+    DVLOG(1) << "Unable to set metrics reporting status to " << enabled;
 
-  if (enabled != update_pref)
-    DVLOG(1) << "Unable to set crash report status to " << enabled;
+  return updated_pref;
+}
 
-  // Only change the pref if GoogleUpdateSettings::GetCollectStatsConsent
-  // succeeds.
-  enabled = update_pref;
-
+// Does the necessary changes for MetricsReportingEnabled changes which needs
+// to be done in the main thread.
+// As arguments this function gets:
+//  |to_update_pref| which indicates what the desired update should be,
+//  |callback_fn| is the callback function to be called in the end
+//  |updated_pref| is the result of attempted update.
+// Update considers to be successful if |to_update_pref| and |updated_pref| are
+// the same.
+void SetMetricsReporting(bool to_update_pref,
+                         const OnMetricsReportingCallbackType callback_fn,
+                         bool updated_pref) {
   metrics::MetricsService* metrics = g_browser_process->metrics_service();
   if (metrics) {
-    if (enabled)
+    if (updated_pref)
       metrics->Start();
     else
       metrics->Stop();
   }
+#if !defined(OS_CHROMEOS)
+  g_browser_process->local_state()->SetBoolean(
+      prefs::kMetricsReportingEnabled, updated_pref);
+#endif
+  if (to_update_pref == updated_pref) {
+    RecordMetricsReportingHistogramValue(updated_pref ?
+        METRICS_REPORTING_ENABLED : METRICS_REPORTING_DISABLED);
+  } else {
+    RecordMetricsReportingHistogramValue(METRICS_REPORTING_ERROR);
+  }
+  if (!callback_fn.is_null())
+    callback_fn.Run(updated_pref);
+}
 
-  return enabled;
+} // namespace
+
+void InitiateMetricsReportingChange(
+    bool enabled,
+    const OnMetricsReportingCallbackType callback_fn) {
+  if (!IsMetricsReportingUserChangable()) {
+    if (!callback_fn.is_null()) {
+      callback_fn.Run(
+          ChromeMetricsServiceAccessor::IsMetricsReportingEnabled());
+    }
+    return;
+  }
+
+  // Posts to FILE thread as SetGoogleUpdateSettings does IO operations.
+  content::BrowserThread::PostTaskAndReplyWithResult(
+      content::BrowserThread::FILE,
+      FROM_HERE,
+      base::Bind(&SetGoogleUpdateSettings, enabled),
+      base::Bind(&SetMetricsReporting, enabled, callback_fn));
 }
+
+bool IsMetricsReportingUserChangable() {
+  const PrefService* pref_service = g_browser_process->local_state();
+
+  const PrefService::Preference* pref =
+      pref_service->FindPreference(prefs::kMetricsReportingEnabled);
+  return pref && !pref->IsManaged();
+}