Use custom tabs in AboutFragment

src/main/scala/com/github/shadowsocks/AboutFragment.scala

@@ -38,9 +38,7 @@ class AboutFragment extends ToolbarFragment {
     web.loadUrl("file:///android_asset/pages/about.html")
     web.setWebViewClient(new WebViewClient() {
       override def shouldOverrideUrlLoading(view: WebView, url: String): Boolean = {
-        try startActivity(new Intent(Intent.ACTION_VIEW, Uri.parse(url))) catch {
-          case _: android.content.ActivityNotFoundException => // Ignore
-        }
+        getActivity.asInstanceOf[MainActivity].launchUrl(url)
         true
       }
     })

src/main/scala/com/github/shadowsocks/MainActivity.scala

@@ -89,6 +89,9 @@ class MainActivity extends Activity with ServiceBoundContext with Drawer.OnDrawe
   private lazy val customTabsIntent = new CustomTabsIntent.Builder()
     .setToolbarColor(ContextCompat.getColor(this, R.color.material_primary_500))
     .build()
+  def launchUrl(url: String): Unit = try customTabsIntent.launchUrl(this, Uri.parse(url)) catch {
+    case _: ActivityNotFoundException => // Ignore
+  }
 
   // Services
   var state: Int = _
@@ -374,7 +377,7 @@ class MainActivity extends Activity with ServiceBoundContext with Drawer.OnDrawe
       case DRAWER_ABOUT =>
         app.track(TAG, "about")
         displayFragment(aboutFragment)
-      case DRAWER_FAQ => customTabsIntent.launchUrl(this, Uri.parse(getString(R.string.faq_url)))
+      case DRAWER_FAQ => launchUrl(getString(R.string.faq_url))
     }
     true  // unexpected cases will throw exception
   }