Use PreloadCheckGroup in ExtensionInstallChecker. Make RequirementsChecker a PreloadCheck.

extensions/browser/api/management/management_api.cc

Index: extensions/browser/api/management/management_api.cc
diff --git a/extensions/browser/api/management/management_api.cc b/extensions/browser/api/management/management_api.cc
index c723341f9c23061cf402f00d88cabe2537114dad..a33130963a1e091cef85e10f1102752c72ad4c7b 100644
--- a/extensions/browser/api/management/management_api.cc
+++ b/extensions/browser/api/management/management_api.cc
@@ -18,7 +18,6 @@
 #include "base/metrics/histogram.h"
 #include "base/single_thread_task_runner.h"
 #include "base/strings/string_number_conversions.h"
-#include "base/strings/string_util.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "build/build_config.h"
@@ -447,9 +446,9 @@ ExtensionFunction::ResponseAction ManagementSetEnabledFunction::Run() {
     if (prefs->GetDisableReasons(extension_id_) &
             Extension::DISABLE_UNSUPPORTED_REQUIREMENT) {
       // Recheck the requirements.
-      requirements_checker_ = delegate->CreateRequirementsChecker();
-      requirements_checker_->Check(
-          extension,
+      requirements_checker_ =
+          base::MakeUnique<extensions::RequirementsChecker>(extension);
+      requirements_checker_->Start(
           base::Bind(&ManagementSetEnabledFunction::OnRequirementsChecked,
                      this));  // This bind creates a reference.
       return RespondLater();
@@ -478,7 +477,7 @@ void ManagementSetEnabledFunction::OnInstallPromptDone(bool did_accept) {
 }
 
 void ManagementSetEnabledFunction::OnRequirementsChecked(
-    const std::vector<std::string>& requirements_errors) {
+    PreloadCheck::Errors requirements_errors) {
   if (requirements_errors.empty()) {
     ManagementAPI::GetFactoryInstance()->Get(browser_context())->GetDelegate()->
         EnableExtension(browser_context(), extension_id_);
@@ -486,7 +485,7 @@ void ManagementSetEnabledFunction::OnRequirementsChecked(
   } else {
     // TODO(devlin): Should we really be noisy here all the time?
     Respond(Error(keys::kMissingRequirementsError,
-                  base::JoinString(requirements_errors, " ")));
+                  base::UTF16ToUTF8(requirements_checker_->GetErrorMessage())));
   }
 }