Move StringImplementation from coreimpl to core as _StringImpl.

lib/compiler/implementation/lib/coreimpl_patch.dart

Index: lib/compiler/implementation/lib/coreimpl_patch.dart
diff --git a/lib/compiler/implementation/lib/coreimpl_patch.dart b/lib/compiler/implementation/lib/coreimpl_patch.dart
index 79f1403792fdd67287b503cd939b6c6491e92bf3..4ef493e0de7c6d6dda472c18f9524102af38d262 100644
--- a/lib/compiler/implementation/lib/coreimpl_patch.dart
+++ b/lib/compiler/implementation/lib/coreimpl_patch.dart
@@ -4,55 +4,6 @@
 
 // Patch file for dart:coreimpl classes.
 
-// Patch for String implementation.
-// TODO(ager): Split out into date_patch.dart and allow #source
-// in patch files?
-patch class StringImplementation {
-  patch static String _fromCharCodes(List<int> charCodes) {
-    checkNull(charCodes);
-    if (!isJsArray(charCodes)) {
-      if (charCodes is !List) throw new ArgumentError(charCodes);
-      charCodes = new List.from(charCodes);
-    }
-    return Primitives.stringFromCharCodes(charCodes);
-  }
-
-  patch String join(List<String> strings, String separator) {
-    checkNull(strings);
-    checkNull(separator);
-    if (separator is !String) throw new ArgumentError(separator);
-    return stringJoinUnchecked(_toJsStringArray(strings), separator);
-  }
-
-  patch String concatAll(List<String> strings) {
-    return stringJoinUnchecked(_toJsStringArray(strings), "");
-  }
-
-  static List _toJsStringArray(List<String> strings) {
-    checkNull(strings);
-    var array;
-    final length = strings.length;
-    if (isJsArray(strings)) {
-      array = strings;
-      for (int i = 0; i < length; i++) {
-        final string = strings[i];
-        checkNull(string);
-        if (string is !String) throw new ArgumentError(string);
-      }
-    } else {
-      array = new List(length);
-      for (int i = 0; i < length; i++) {
-        final string = strings[i];
-        checkNull(string);
-        if (string is !String) throw new ArgumentError(string);
-        array[i] = string;
-      }
-    }
-    return array;
-  }
-}
-
-
 // Patch for RegExp implementation.
 // TODO(ager): Split out into regexp_patch.dart and allow #source in
 // patch files?