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

ui/android/java/src/org/chromium/ui/base/LocalizationUtils.java

Index: ui/android/java/src/org/chromium/ui/base/LocalizationUtils.java
diff --git a/ui/android/java/src/org/chromium/ui/base/LocalizationUtils.java b/ui/android/java/src/org/chromium/ui/base/LocalizationUtils.java
index e163b3f75db5cbff8a8151e78ed67646ba864c92..0dc17544bee9a38ab068d6eae65f12ac0675e429 100644
--- a/ui/android/java/src/org/chromium/ui/base/LocalizationUtils.java
+++ b/ui/android/java/src/org/chromium/ui/base/LocalizationUtils.java
@@ -66,6 +66,7 @@ public class LocalizationUtils {
      * @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);
     }