[debugger] remove some dead code.

src/debug/debug.cc

 // Copyright 2012 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.h"
 
 #include "src/api.h"
 #include "src/arguments.h"
 #include "src/bootstrapper.h"
 #include "src/code-stubs.h"
@@ skipping 282 matching lines @@
   // Debugger statement always calls debugger. No need to modify it.
   if (IsDebuggerStatement()) return;
 
   DCHECK(IsDebugBreakSlot());
   DebugCodegen::ClearDebugBreakSlot(debug_info_->GetIsolate(), pc());
   DCHECK(!IsDebugBreak());
 }
 
 
 bool BreakLocation::IsDebugBreak() const {
-  if (IsDebugBreakSlot()) {
-    return rinfo().IsPatchedDebugBreakSlotSequence();
-  }
-  return false;
+  if (IsDebuggerStatement()) return false;
+  DCHECK(IsDebugBreakSlot());
+  return rinfo().IsPatchedDebugBreakSlotSequence();
 }
 
 
 Handle<Object> BreakLocation::BreakPointObjects() const {
   return debug_info_->GetBreakPointObjects(pc_offset_);
 }
 
 
 void DebugFeatureTracker::Track(DebugFeatureTracker::Feature feature) {
   uint32_t mask = 1 << feature;
@@ skipping 663 matching lines @@
         break_location->code()->SourceStatementPosition(frame->pc());
     return thread_local_.last_fp_ == frame->UnpaddedFP() &&
         thread_local_.last_statement_position_ == current_statement_position;
   }
 
   // No step next action - don't continue.
   return false;
 }
 
 
-// Check whether the code object at the specified address is a debug break code
-// object.
-bool Debug::IsDebugBreak(Address addr) {
-  Code* code = Code::GetCodeFromTargetAddress(addr);
-  return code->is_debug_stub();
-}
-
-
 // Simple function for returning the source positions for active break points.
 Handle<Object> Debug::GetSourceBreakLocations(
     Handle<SharedFunctionInfo> shared,
     BreakPositionAlignment position_alignment) {
   Isolate* isolate = shared->GetIsolate();
   Heap* heap = isolate->heap();
   if (!shared->HasDebugInfo()) {
     return Handle<Object>(heap->undefined_value(), isolate);
   }
   Handle<DebugInfo> debug_info(shared->GetDebugInfo());
@@ skipping 1499 matching lines @@
 }
 
 
 void LockingCommandMessageQueue::Clear() {
   base::LockGuard<base::Mutex> lock_guard(&mutex_);
   queue_.Clear();
 }
 
 }  // namespace internal
 }  // namespace v8