Move native "enable-webapk" check to ChromeWebApkHost.

chrome/browser/android/webapk/chrome_webapk_host.h

+// Copyright 2016 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.
+
+#ifndef CHROME_BROWSER_ANDROID_WEBAPK_CHROME_WEBAPK_HOST_H_
+#define CHROME_BROWSER_ANDROID_WEBAPK_CHROME_WEBAPK_HOST_H_
+
+#include "base/macros.h"
+
+// ChromeWebApkHost is the C++ counterpart of org.chromium.chrome.browser's
+// ChromeWebApkHost in Java.
+class ChromeWebApkHost {
+ public:
+  // Returns whether the "enalbe-webapk" is turned on.
+  static bool AreWebApkEnabled();
+
+ private:
+  DISALLOW_IMPLICIT_CONSTRUCTORS(ChromeWebApkHost);
+};
+
+#endif  // CHROME_BROWSER_ANDROID_WEBAPK_CHROME_WEBAPK_HOST_H_