Revert "VM(RegExp): Allow OSR optimization of RegExp :matcher functions."

runtime/vm/regexp_assembler.h

 // Copyright (c) 2014, 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 RUNTIME_VM_REGEXP_ASSEMBLER_H_
 #define RUNTIME_VM_REGEXP_ASSEMBLER_H_
 
 #include "vm/assembler.h"
 #include "vm/intermediate_language.h"
 #include "vm/object.h"
@@ skipping 135 matching lines @@
                                      BlockLabel* on_in_range) = 0;
   virtual void CheckCharacterNotInRange(uint16_t from,
                                         uint16_t to,  // Both inclusive.
                                         BlockLabel* on_not_in_range) = 0;
 
   // The current character (modulus the kTableSize) is looked up in the byte
   // array, and if the found byte is non-zero, we jump to the on_bit_set label.
   virtual void CheckBitInTable(const TypedData& table,
                                BlockLabel* on_bit_set) = 0;
 
-  // Checks for pre-emption and serves as an OSR entry.
-  virtual void CheckPreemption(bool is_backtrack) {}
-
   // Checks whether the given offset from the current position is before
   // the end of the string.  May overwrite the current character.
   virtual void CheckPosition(intptr_t cp_offset, BlockLabel* on_outside_input) {
     LoadCurrentCharacter(cp_offset, on_outside_input, true);
   }
   // Check whether a standard/default character class matches the current
   // character. Returns false if the type of special character class does
   // not have custom support.
   // May clobber the current loaded character.
   virtual bool CheckSpecialCharacterClass(uint16_t type,
@@ skipping 60 matching lines @@
 
  private:
   bool slow_safe_compiler_;
   bool global_mode_;
   Zone* zone_;
 };
 
 }  // namespace dart
 
 #endif  // RUNTIME_VM_REGEXP_ASSEMBLER_H_