Implement stub functions

Implement stub functions to prevent build breakage related to
changes in android.webkit classes.

Bug: 10237116
Change-Id: I8723446925277eaaa8804f13636da1d93d552d78
diff --git a/chromium/java/com/android/webview/chromium/WebViewChromium.java b/chromium/java/com/android/webview/chromium/WebViewChromium.java
index 6cf4238..ecc197f 100644
--- a/chromium/java/com/android/webview/chromium/WebViewChromium.java
+++ b/chromium/java/com/android/webview/chromium/WebViewChromium.java
@@ -55,6 +55,8 @@
 import android.webkit.ValueCallback;
 import android.webkit.WebBackForwardList;
 import android.webkit.WebChromeClient;
+import android.webkit.WebMessage;
+import android.webkit.WebMessagePort;
 import android.webkit.WebSettings;
 import android.webkit.WebView;
 import android.webkit.WebViewClient;
@@ -1412,6 +1414,16 @@
     }
 
     @Override
+    public WebMessagePort[] createWebMessageChannel() {
+        throw new UnsupportedOperationException();
+    }
+
+    @Override
+    public void postMessageToMainFrame(WebMessage message, Uri targetOrigin) {
+        throw new UnsupportedOperationException();
+    }
+
+    @Override
     public WebSettings getSettings() {
         return mWebSettings;
     }