Preserve the contents of Dart strings with unmatched surrogate halfs by avoiding a UTF16 -> UTF8

runtime/vm/json_stream.h

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef VM_JSON_STREAM_H_
 #define VM_JSON_STREAM_H_
 
 #include "include/dart_api.h"  // for Dart_Port
 #include "platform/json.h"
 #include "vm/allocation.h"
@@ skipping 75 matching lines @@
   void PrintValue(double d);
   void PrintValue(const char* s);
   void PrintValue(const char* s, intptr_t len);
   void PrintValueNoEscape(const char* s);
   void PrintfValue(const char* format, ...) PRINTF_ATTRIBUTE(2, 3);
   void PrintValue(const Object& o, bool ref = true);
   void PrintValue(SourceBreakpoint* bpt);
   void PrintValue(const DebuggerEvent* event);
   void PrintValue(Metric* metric);
   void PrintValue(Isolate* isolate, bool ref = true);
+  bool PrintValueStr(const String& s, intptr_t limit);
 
   void PrintPropertyBool(const char* name, bool b);
   void PrintProperty(const char* name, intptr_t i);
   void PrintProperty64(const char* name, int64_t i);
   void PrintProperty(const char* name, double d);
   void PrintProperty(const char* name, const char* s);
-  void PrintProperty(const char* name, const char* s, intptr_t len);
+  bool PrintPropertyStr(const char* name, const String& s, intptr_t limit);
   void PrintPropertyNoEscape(const char* name, const char* s);
   void PrintfProperty(const char* name, const char* format, ...)
   PRINTF_ATTRIBUTE(3, 4);
   void PrintProperty(const char* name, const Object& o, bool ref = true);
 
   void PrintProperty(const char* name, const DebuggerEvent* event);
   void PrintProperty(const char* name, SourceBreakpoint* bpt);
   void PrintProperty(const char* name, Metric* metric);
   void PrintProperty(const char* name, Isolate* isolate);
   void PrintPropertyName(const char* name);
   void PrintCommaIfNeeded();
   bool NeedComma();
 
+  bool AddDartString(const String& s, intptr_t limit);
   void AddEscapedUTF8String(const char* s);
   void AddEscapedUTF8String(const char* s, intptr_t len);
 
   intptr_t nesting_level() const { return open_objects_; }
 
   intptr_t open_objects_;
   TextBuffer buffer_;
   Dart_Port reply_port_;
   const char* command_;
   const char** arguments_;
@@ skipping 30 matching lines @@
   }
   void AddProperty64(const char* name, int64_t i) const {
     stream_->PrintProperty64(name, i);
   }
   void AddProperty(const char* name, double d) const {
     stream_->PrintProperty(name, d);
   }
   void AddProperty(const char* name, const char* s) const {
     stream_->PrintProperty(name, s);
   }
-  void AddProperty(const char* name, const char* s, intptr_t len) const {
-    stream_->PrintProperty(name, s, len);
+  bool AddPropertyStr(const char* name,
+                      const String& s,
+                      intptr_t limit = -1) const {
+    return stream_->PrintPropertyStr(name, s, limit);
   }
   void AddPropertyNoEscape(const char* name, const char* s) const {
     stream_->PrintPropertyNoEscape(name, s);
   }
   void AddProperty(const char* name, const Object& obj, bool ref = true) const {
     stream_->PrintProperty(name, obj, ref);
   }
   void AddProperty(const char* name, const DebuggerEvent* event) const {
     stream_->PrintProperty(name, event);
   }
@@ skipping 61 matching lines @@
 
   friend class JSONObject;
 
   DISALLOW_ALLOCATION();
   DISALLOW_COPY_AND_ASSIGN(JSONArray);
 };
 
 }  // namespace dart
 
 #endif  // VM_JSON_STREAM_H_