Move current WebView provider from Settings.Secure to Settings.Global

The current WebView provider is not user-specific and should therefore
be stored as a Global rather than a Secure setting.

Also do some code cleaning including a fix in WebViewProviderInfo to
always fetch up-to-date information about whether a webview
implementation package is enabled.

Bug: 27142972
Change-Id: I4d4b8fca775e97980fb5c34313be6d82472e7d33
diff --git a/core/java/android/provider/Settings.java b/core/java/android/provider/Settings.java
index 7830142..9b5d865 100755
--- a/core/java/android/provider/Settings.java
+++ b/core/java/android/provider/Settings.java
@@ -5907,13 +5907,6 @@
                 "camera_double_tap_power_gesture_disabled";
 
         /**
-         * Name of the package used as WebView provider (if unset the provider is instead determined
-         * by the system).
-         * @hide
-         */
-        public static final String WEBVIEW_PROVIDER = "webview_provider";
-
-        /**
          * This are the settings to be backed up.
          *
          * NOTE: Settings are backed up and restored in the order they appear
@@ -6940,6 +6933,13 @@
         public static final String WEBVIEW_DATA_REDUCTION_PROXY_KEY =
                 "webview_data_reduction_proxy_key";
 
+        /**
+         * Name of the package used as WebView provider (if unset the provider is instead determined
+         * by the system).
+         * @hide
+         */
+        public static final String WEBVIEW_PROVIDER = "webview_provider";
+
        /**
         * Whether Wifi display is enabled/disabled
         * 0=disabled. 1=enabled.