Replace ExtensionInstallChecker with generic PreloadCheckGroup

extensions/browser/preload_check_group.cc

Index: extensions/browser/preload_check_group.cc
diff --git a/extensions/browser/preload_check_group.cc b/extensions/browser/preload_check_group.cc
new file mode 100644
index 0000000000000000000000000000000000000000..0f849771d9c27e9f714088c86b17656621d5f296
--- /dev/null
+++ b/extensions/browser/preload_check_group.cc
@@ -0,0 +1,60 @@
+// Copyright 2017 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 "extensions/browser/preload_check_group.h"
+
+#include "base/bind.h"
+#include "base/callback_helpers.h"
+#include "base/memory/ref_counted.h"
+#include "extensions/common/extension.h"
+
+namespace extensions {
+
+PreloadCheckGroup::PreloadCheckGroup()
+    : PreloadCheck(nullptr), weak_ptr_factory_(this) {}
+
+PreloadCheckGroup::~PreloadCheckGroup() {}
+
+void PreloadCheckGroup::AddCheck(PreloadCheck* check) {
+  DCHECK(running_checks_ == 0);
+  checks_.push_back(check);
+}
+
+void PreloadCheckGroup::Start(ResultCallback callback) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  DCHECK(running_checks_ == 0);

[Devlin, 2017/04/04 01:37:26]

nit: DCHECK_EQ(0, running_checks_)

[michaelpg, 2017/04/04 21:41:29]

Done.

+
+  callback_ = std::move(callback);
+  running_checks_ = checks_.size();
+  for (auto* check : checks_) {
+    check->Start(base::Bind(&PreloadCheckGroup::OnCheckComplete,
+                            weak_ptr_factory_.GetWeakPtr()));
+    // Synchronous checks may fail immediately.
+    if (running_checks_ == 0)
+      return;
+  }
+}
+
+void PreloadCheckGroup::OnCheckComplete(Errors errors) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  errors_.insert(errors.begin(), errors.end());
+  running_checks_--;
+  MaybeInvokeCallback();
+}
+
+void PreloadCheckGroup::MaybeInvokeCallback() {
+  // Only invoke callback if all checks are complete, or if there was at least
+  // one failure and |stop_on_first_error_| is true.
+  if (running_checks_ > 0 && (errors_.empty() || !stop_on_first_error_))
+    return;
+
+  // If we are failing fast, discard any pending results.
+  weak_ptr_factory_.InvalidateWeakPtrs();
+  running_checks_ = 0;
+
+  DCHECK(!callback_.is_null());
+  base::ResetAndReturn(&callback_).Run(errors_);
+}
+
+}  // namespace extensions