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

ui/android/java/src/org/chromium/ui/base/LocalizationUtils.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.ui.base;
 
 import android.content.res.Configuration;
 import android.view.View;
 
 import org.chromium.base.ApiCompatibilityUtils;
@@ skipping 48 matching lines @@
 
         return sIsLayoutRtl.booleanValue();
     }
 
     /**
      * Jni binding to base::i18n::GetFirstStrongCharacterDirection
      * @param string String to decide the direction.
      * @return One of the UNKNOWN_DIRECTION, RIGHT_TO_LEFT, and LEFT_TO_RIGHT.
      */
     public static int getFirstStrongCharacterDirection(String string) {
+        assert string != null;
         return nativeGetFirstStrongCharacterDirection(string);
     }
 
     /**
      * Jni binding to ui::TimeFormat::TimeRemaining. Converts milliseconds to
      * time remaining format : "3 mins left", "2 days left".
      * @param timeInMillis time in milliseconds
      * @return time remaining
      */
     public static String getDurationString(long timeInMillis) {
         return nativeGetDurationString(timeInMillis);
     }
 
     private static native int nativeGetFirstStrongCharacterDirection(String string);
 
     private static native String nativeGetDurationString(long timeInMillis);
 }