Cache the parsed result of WebView provider config xml

BUG: 27736084
Change-Id: I3665a5fd4777d22c6f217b358195edbeaad3bb1d
diff --git a/services/core/java/com/android/server/webkit/WebViewUpdateService.java b/services/core/java/com/android/server/webkit/WebViewUpdateService.java
index bbb4951..9b971e0 100644
--- a/services/core/java/com/android/server/webkit/WebViewUpdateService.java
+++ b/services/core/java/com/android/server/webkit/WebViewUpdateService.java
@@ -55,7 +55,7 @@
 
     public WebViewUpdateService(Context context) {
         super(context);
-        mImpl = new WebViewUpdateServiceImpl(context, new SystemImpl());
+        mImpl = new WebViewUpdateServiceImpl(context, SystemImpl.getInstance());
     }
 
     @Override