Implement faster splitting with empty string as pattern. Add special native for computing substring…

runtime/vm/object.h

 // Copyright (c) 2012, 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_OBJECT_H_
 #define VM_OBJECT_H_
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "platform/utils.h"
@@ skipping 3967 matching lines @@
                                intptr_t len,
                                Heap::Space space);
   static RawOneByteString* New(const uint16_t* characters,
                                intptr_t len,
                                Heap::Space space);
   static RawOneByteString* New(const int32_t* characters,
                                intptr_t len,
                                Heap::Space space);
   static RawOneByteString* New(const String& str,
                                Heap::Space space);
+  static RawOneByteString* New(const String& other,
+                               intptr_t other_start_index,
+                               intptr_t other_len,
+                               Heap::Space space);
 
   static RawOneByteString* Concat(const String& str1,
                                   const String& str2,
                                   Heap::Space space);
   static RawOneByteString* ConcatAll(const Array& strings,
                                      intptr_t len,
                                      Heap::Space space);
 
   static RawOneByteString* Transform(int32_t (*mapping)(int32_t ch),
                                      const String& str,
@@ skipping 1970 matching lines @@
     if (this->CharAt(i) != str.CharAt(begin_index + i)) {
       return false;
     }
   }
   return true;
 }
 
 }  // namespace dart
 
 #endif  // VM_OBJECT_H_