Remove deprecated string features.

runtime/bin/process_patch.dart

Index: runtime/bin/process_patch.dart
diff --git a/runtime/bin/process_patch.dart b/runtime/bin/process_patch.dart
index edc29e294c144f62518e7a32dd1fdb5dc0226fe6..93d8bc5c890d0fa33fe2295aa21c663cbfbcf544 100644
--- a/runtime/bin/process_patch.dart
+++ b/runtime/bin/process_patch.dart
@@ -105,14 +105,14 @@ class _ProcessImpl extends NativeFieldWrapperClass1 implements Process {
 
       // Replace any number of '\' followed by '"' with
       // twice as many '\' followed by '\"'.
-      var backslash = '\\'.charCodeAt(0);
+      var backslash = '\\'.codeUnitAt(0);
       var sb = new StringBuffer();
       var nextPos = 0;
       var quotePos = argument.indexOf('"', nextPos);
       while (quotePos != -1) {
         var numBackslash = 0;
         var pos = quotePos - 1;
-        while (pos >= 0 && argument.charCodeAt(pos) == backslash) {
+        while (pos >= 0 && argument.codeUnitAt(pos) == backslash) {
           numBackslash++;
           pos--;
         }
@@ -132,7 +132,7 @@ class _ProcessImpl extends NativeFieldWrapperClass1 implements Process {
       sb = new StringBuffer('"');
       sb.add(result);
       nextPos = argument.length - 1;
-      while (argument.charCodeAt(nextPos) == backslash) {
+      while (argument.codeUnitAt(nextPos) == backslash) {
         sb.add('\\');
         nextPos--;
       }