Update NullWebView interface to match real WebView.

The real WebView is created via a static factory method now; add the
corresponding method to NullWebViewFactoryProvider so they can be
created uniformly.

Bug: 37645436
Test: cts-tradefed run commandAndExit cts -m CtsWidgetTestCases -t android.widget.cts.TextViewTest
Change-Id: Ic8e1dd84e3b78d3a0173ff13e5e849c224a3cd78

nullwebview/java/com/android/webview/nullwebview/NullWebViewFactoryProvider.java

diff --git a/nullwebview/java/com/android/webview/nullwebview/NullWebViewFactoryProvider.java b/nullwebview/java/com/android/webview/nullwebview/NullWebViewFactoryProvider.java
index 8132a34..ed12446 100644
--- a/nullwebview/java/com/android/webview/nullwebview/NullWebViewFactoryProvider.java
+++ b/nullwebview/java/com/android/webview/nullwebview/NullWebViewFactoryProvider.java
@@ -31,6 +31,10 @@
 
 public class NullWebViewFactoryProvider implements WebViewFactoryProvider {
 
+    public static WebViewFactoryProvider create(WebViewDelegate delegate) {
+        return new NullWebViewFactoryProvider(delegate);
+    }
+
     public NullWebViewFactoryProvider(WebViewDelegate delegate) {
     }