Implement rewind: drop one or more frames from the debugger.

runtime/vm/raw_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 RUNTIME_VM_RAW_OBJECT_H_
 #define RUNTIME_VM_RAW_OBJECT_H_
 
 #include "platform/assert.h"
 #include "vm/atomic.h"
 #include "vm/globals.h"
@@ skipping 1179 matching lines @@
 
 
 class RawPcDescriptors : public RawObject {
  public:
   enum Kind {
     kDeopt = 1,                            // Deoptimization continuation point.
     kIcCall = kDeopt << 1,                 // IC call.
     kUnoptStaticCall = kIcCall << 1,       // Call to a known target via stub.
     kRuntimeCall = kUnoptStaticCall << 1,  // Runtime call.
     kOsrEntry = kRuntimeCall << 1,         // OSR entry point in unopt. code.
-    kOther = kOsrEntry << 1,
+    kRewind = kOsrEntry << 1,              // Call rewind target address.
+    kOther = kRewind << 1,
     kLastKind = kOther,
     kAnyKind = -1
   };
 
   class MergedKindTry {
    public:
     // Most of the time try_index will be small and merged field will fit into
     // one byte.
     static intptr_t Encode(intptr_t kind, intptr_t try_index) {
       intptr_t kind_shift = Utils::ShiftForPowerOfTwo(kind);
@@ skipping 1183 matching lines @@
   COMPILE_ASSERT(kExternalTypedDataInt8ArrayCid ==
                  kTypedDataInt8ArrayViewCid + 15);
   COMPILE_ASSERT(kByteBufferCid == kExternalTypedDataInt8ArrayCid + 14);
   COMPILE_ASSERT(kNullCid == kByteBufferCid + 1);
   return (kNullCid - kTypedDataInt8ArrayCid);
 }
 
 }  // namespace dart
 
 #endif  // RUNTIME_VM_RAW_OBJECT_H_