[debugger] remove some dead code.

src/debug/debug-frames.cc

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/debug/debug-frames.h"
 
 #include "src/frames-inl.h"
 
 namespace v8 {
 namespace internal {
@@ skipping 27 matching lines @@
   }
 }
 
 
 int FrameInspector::GetParametersCount() {
   return is_optimized_ ? deoptimized_frame_->parameters_count()
                        : frame_->ComputeParametersCount();
 }
 
 
-int FrameInspector::expression_count() {
-  return deoptimized_frame_->expression_count();
-}
-
-
 Object* FrameInspector::GetFunction() {
   return is_optimized_ ? deoptimized_frame_->GetFunction() : frame_->function();
 }
 
 
 Object* FrameInspector::GetParameter(int index) {
   return is_optimized_ ? deoptimized_frame_->GetParameter(index)
                        : frame_->GetParameter(index);
 }
 
@@ skipping 148 matching lines @@
       if (!frames[i].function()->shared()->IsSubjectToDebugging()) continue;
       if (++count == index) return i;
     }
   }
   return -1;
 }
 
 
 }  // namespace internal
 }  // namespace v8