[Android WebView] Fix some findbugs warnings.

android_webview/java/src/org/chromium/android_webview/AwContents.java

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 package org.chromium.android_webview;
 
 import android.graphics.Bitmap;
 import android.net.http.SslCertificate;
 import android.os.AsyncTask;
 import android.os.Handler;
@@ skipping 63 matching lines @@
     private class IoThreadClientHandler extends Handler {
         public static final int MSG_SHOULD_INTERCEPT_REQUEST = 1;
 
         @Override
         public void handleMessage(Message msg) {
             switch(msg.what) {
                 case MSG_SHOULD_INTERCEPT_REQUEST:
                     final String url = (String)msg.obj;
                     AwContents.this.mContentsClient.onLoadResource(url);
                     break;
+                default:
+                    throw new IllegalStateException(
+                            "IoThreadClientHandler: unhandled message " + msg.what);
             }
         }
     }
 
     private class IoThreadClientImpl implements AwContentsIoThreadClient {
         // Called on the IO thread.
         @Override
         public InterceptedRequestData shouldInterceptRequest(final String url) {
             InterceptedRequestData interceptedRequestData =
                 AwContents.this.mContentsClient.shouldInterceptRequest(url);
@@ skipping 365 matching lines @@
     private native void nativeSetInterceptNavigationDelegate(int nativeAwContents,
             InterceptNavigationDelegate navigationInterceptionDelegate);
 
     private native int nativeFindAllSync(int nativeAwContents, String searchString);
     private native void nativeFindAllAsync(int nativeAwContents, String searchString);
     private native void nativeFindNext(int nativeAwContents, boolean forward);
     private native void nativeClearMatches(int nativeAwContents);
     private native void nativeClearCache(int nativeAwContents, boolean includeDiskFiles);
     private native byte[] nativeGetCertificate(int nativeAwContents);
 }