Do Arabic shaping earlier before measuring the text so that it gets laid out correctly. Bugs 117041, 138097. r=ftang, sr=waterson

intl/unicharutil/util/nsBidiUtils.cpp

@@ -256,7 +256,7 @@ nsresult ArabicShaping(const PRUnichar* aString, PRUint32 aLen,
                        PRBool aInputLogical, PRBool aOutputLogical)
 {
   nsAutoString tempString(aString);
-  PRUnichar *tempBuf = (PRUnichar*)tempString.get();
+  PRUnichar *tempBuf = NS_CONST_CAST(PRUnichar*, tempString.get());
   if (aInputLogical) {
     ReverseString(tempBuf, aLen);
   }
@@ -318,7 +318,8 @@ nsresult ArabicShaping(const PRUnichar* aString, PRUint32 aLen,
       for(i=0;i<8;i++) {
         if(key == gArabicLigatureMap[i]) {
           done = PR_TRUE;
-          *lDest++ = 0x200B;//ZERO WIDTH SPACE
+          // lam and alef in the source are mapped to a lam-alef ligature in the
+          // destination, so lSrc is incremented by 2 here
           *lDest++ = 0xFEF5 + i;
           lSrc+=2;
           break;