ChromeOS: use GoogleUpdateSettings::GetCollectStatsConsent on blocking thread.

This is an update to https://chromium-review.googlesource.com/783707 that
ensures that blocking GetCollectStatsConsent is used only on a blocking thread.

Bug: 782641
Change-Id: I5629e00616f1ab24b4a63f1c3433f683370c3239
Reviewed-on: https://chromium-review.googlesource.com/802764
Commit-Queue: Alexander Alekseev <alemate@chromium.org>
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#521055}

chrome/browser/ui/webui/chromeos/login/gaia_screen_handler.cc

@@ -216,6 +216,11 @@ bool IsOnline(NetworkPortalDetector::CaptivePortalStatus status) {
   return status == NetworkPortalDetector::CAPTIVE_PORTAL_STATUS_ONLINE;
 }
 
+void GetVersionAndConsent(std::string* out_version, bool* out_consent) {
+  *out_version = version_loader::GetVersion(version_loader::VERSION_SHORT);
+  *out_consent = GoogleUpdateSettings::GetCollectStatsConsent();
+}
+
 }  // namespace
 
 // A class that's used to specify the way how Gaia should be loaded.
@@ -293,16 +298,24 @@ void GaiaScreenHandler::DisableRestrictiveProxyCheckForTest() {
 }
 
 void GaiaScreenHandler::LoadGaia(const GaiaContext& context) {
-  base::PostTaskWithTraitsAndReplyWithResult(
-      FROM_HERE, {base::MayBlock(), base::TaskPriority::BACKGROUND},
-      base::Bind(&version_loader::GetVersion, version_loader::VERSION_SHORT),
-      base::Bind(&GaiaScreenHandler::LoadGaiaWithVersion,
-                 weak_factory_.GetWeakPtr(), context));
-}
-
-void GaiaScreenHandler::LoadGaiaWithVersion(
+  std::unique_ptr<std::string> version = std::make_unique<std::string>();
+  std::unique_ptr<bool> consent = std::make_unique<bool>();
+  base::OnceClosure get_version_and_consent =
+      base::BindOnce(&GetVersionAndConsent, base::Unretained(version.get()),
+                     base::Unretained(consent.get()));
+  base::OnceClosure load_gaia = base::BindOnce(
+      &GaiaScreenHandler::LoadGaiaWithVersionAndConsent,
+      weak_factory_.GetWeakPtr(), context, base::Owned(version.release()),
+      base::Owned(consent.release()));
+  base::PostTaskWithTraitsAndReply(
+      FROM_HERE, {base::MayBlock(), base::TaskPriority::USER_VISIBLE},
+      std::move(get_version_and_consent), std::move(load_gaia));
+}
+
+void GaiaScreenHandler::LoadGaiaWithVersionAndConsent(
     const GaiaContext& context,
-    const std::string& platform_version) {
+    const std::string* platform_version,
+    const bool* collect_stats_consent) {
   // Start a new session with SigninPartitionManager, generating a a unique
   // StoragePartition.
   login::SigninPartitionManager* signin_partition_manager =
@@ -359,8 +372,8 @@ void GaiaScreenHandler::LoadGaiaWithVersion(
   params.SetString("clientId",
                    GaiaUrls::GetInstance()->oauth2_chrome_client_id());
   params.SetString("clientVersion", version_info::GetVersionNumber());
-  if (!platform_version.empty())
-    params.SetString("platformVersion", platform_version);
+  if (!platform_version->empty())
+    params.SetString("platformVersion", *platform_version);
   params.SetString("releaseChannel", chrome::GetChannelString());
   params.SetString("endpointGen", kEndpointGen);
 
@@ -383,7 +396,7 @@ void GaiaScreenHandler::LoadGaiaWithVersion(
   }
   // We only send |chromeos_board| Gaia URL parameter if user has opted into
   // sending device statistics.
-  if (GoogleUpdateSettings::GetCollectStatsConsent())
+  if (*collect_stats_consent)
     params.SetString("lsbReleaseBoard", base::SysInfo::GetLsbReleaseBoard());
   params.SetString("webviewPartitionName",
                    signin_partition_manager->GetCurrentStoragePartitionName());

chrome/browser/ui/webui/chromeos/login/gaia_screen_handler.h

@@ -58,9 +58,11 @@ class GaiaScreenHandler : public BaseScreenHandler,
 
   void LoadGaia(const GaiaContext& context);
 
-  // Callback that loads GAIA after version information has been retrieved.
-  void LoadGaiaWithVersion(const GaiaContext& context,
-                           const std::string& platform_version);
+  // Callback that loads GAIA after version and stat consent information has
+  // been retrieved.
+  void LoadGaiaWithVersionAndConsent(const GaiaContext& context,
+                                     const std::string* platform_version,
+                                     const bool* collect_stats_consent);
 
   // Sends request to reload Gaia. If |force_reload| is true, request
   // will be sent in any case, otherwise it will be sent only when Gaia is