Bug 389437. Handle searching for word breaks when starting at the end of the available text. r=smontagu,a=damon

intl/lwbrk/src/nsSampleWordBreaker.cpp

@@ -163,6 +163,8 @@ PRInt32 nsSampleWordBreaker::NextWord(
 {
   PRInt8 c1, c2;
   PRUint32 cur = aPos;
+  if (cur == aLen)
+    return NS_WORDBREAKER_NEED_MORE_TEXT;
   c1 = this->GetClass(aText[cur]);
  
   for(cur++; cur <aLen; cur++)
@@ -186,6 +188,11 @@ PRInt32 nsSampleWordBreaker::PrevWord(
 {
   PRInt8 c1, c2;
   PRUint32 cur = aPos;
+  if (cur == aLen) {
+    if (cur == 0)
+      return NS_WORDBREAKER_NEED_MORE_TEXT;
+    --cur;
+  }
   c1 = this->GetClass(aText[cur]);
 
   for(; cur > 0; cur--)