DCHECK that jstring to C++ string conversions don't pass in null.

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

 // Copyright 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.annotation.SuppressLint;
 import android.app.Activity;
 import android.content.ComponentCallbacks2;
 import android.content.Context;
@@ skipping 1329 matching lines @@
 
     public Bitmap getFavicon() {
         if (isDestroyed(WARN)) return null;
         return mFavicon;
     }
 
     private void requestVisitedHistoryFromClient() {
         ValueCallback<String[]> callback = new ValueCallback<String[]>() {
             @Override
             public void onReceiveValue(final String[] value) {
+                if (value != null) {
+                    // Replace null values with empty strings, because they can't be represented as
+                    // native strings.
+                    for (int i = 0; i < value.length; i++) {
+                        if (value[i] == null) value[i] = "";
+                    }
+                }
+
                 ThreadUtils.runOnUiThread(new Runnable() {
                     @Override
                     public void run() {
                         if (!isDestroyed(NO_WARN)) nativeAddVisitedLinks(mNativeAwContents, value);
                     }
                 });
             }
         };
         mContentsClient.getVisitedHistory(callback);
     }
@@ skipping 1946 matching lines @@
             long resources);
 
     private native void nativePostMessageToFrame(long nativeAwContents, String frameId,
             String message, String targetOrigin, int[] msgPorts);
 
     private native void nativeCreateMessageChannel(long nativeAwContents, AwMessagePort[] ports);
 
     private native void nativeGrantFileSchemeAccesstoChildProcess(long nativeAwContents);
     private native void nativeResumeLoadingCreatedPopupWebContents(long nativeAwContents);
 }