Don't double-escape in strings in the VM Service, and don't use \u0000 to determine the string lengt

runtime/vm/object.h

Index: runtime/vm/object.h
diff --git a/runtime/vm/object.h b/runtime/vm/object.h
index 6bef907ae75b4b85787590a7f2be10f3ed827d71..211d5ab050102f88ccafa616d1f5e978bed3886d 100644
--- a/runtime/vm/object.h
+++ b/runtime/vm/object.h
@@ -5573,8 +5573,10 @@ class String : public Instance {
 
   void ToUTF8(uint8_t* utf8_array, intptr_t array_len) const;
 
-  // Produces a quoted, escaped, (possibly) truncated string.
-  const char* ToUserCString(intptr_t max_len) const;
+  const char* ToCString(intptr_t *length) const;
+  const char* ToCStringTruncated(intptr_t max_len,
+                                 bool* did_truncate,
+                                 intptr_t *length) const;
 
   // Copies the string characters into the provided external array
   // and morphs the string object into an external string object.
@@ -5720,9 +5722,6 @@ class String : public Instance {
                            CallbackType new_symbol,
                            Snapshot::Kind kind);
 
-  intptr_t EscapedString(char* buffer, int max_len) const;
-  intptr_t EscapedStringLen(intptr_t tooLong) const;
-
   FINAL_HEAP_OBJECT_IMPLEMENTATION(String, Instance);
 
   friend class Class;