use a more efficient way of iteration

Author: rbri

src/main/java/org/htmlunit/html/serializer/HtmlSerializerInnerOuterText.java

@@ -387,9 +387,9 @@ public void append(final String content, final Mode mode) {
             }
 
             length--;
-            int i = -1;
-            for (char c : content.toCharArray()) {
-                i++;
+            final int contentLenght = content.length();
+            for (int i = 0; i < contentLenght; i++) {
+                char c = content.charAt(i);
 
                 // handle \r
                 if (c == '\r') {

src/main/java/org/htmlunit/html/serializer/HtmlSerializerNormalizedText.java

@@ -638,7 +638,10 @@ public void append(final String content, final Mode mode) {
             }
 
             boolean crFound = false;
-            for (final char c : text.toCharArray()) {
+            final int textLenght = text.length();
+            for (int i = 0; i < textLenght; i++) {
+                final char c = text.charAt(i);
+
                 if (mode == Mode.NORMALIZE) {
                     if (isSpace(c)) {
                         switch (state_) {

src/main/java/org/htmlunit/html/serializer/HtmlSerializerVisibleText.java

@@ -812,9 +812,9 @@ public void append(final String content, final Mode mode) {
             }
 
             length--;
-            int i = -1;
-            for (char c : content.toCharArray()) {
-                i++;
+            final int contentLenght = content.length();
+            for (int i = 0; i < contentLenght; i++) {
+                char c = content.charAt(i);
 
                 // handle \r
                 if (c == '\r') {