[debugger] introduce abstract interface for break location.

src/debug/x64/debug-x64.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.
 
 #if V8_TARGET_ARCH_X64
 
 #include "src/assembler.h"
 #include "src/codegen.h"
 #include "src/debug/debug.h"
 
@@ skipping 33 matching lines @@
   CodePatcher patcher(isolate, pc, kSize);
   Label check_codesize;
   patcher.masm()->bind(&check_codesize);
   patcher.masm()->movp(kScratchRegister, reinterpret_cast<void*>(code->entry()),
                        Assembler::RelocInfoNone());
   patcher.masm()->call(kScratchRegister);
   // Check that the size of the code generated is as expected.
   DCHECK_EQ(kSize, patcher.masm()->SizeOfCodeGeneratedSince(&check_codesize));
 }
 
+bool DebugCodegen::DebugBreakSlotIsPatched(Address pc) {
+  return !Assembler::IsNop(pc);
+}
 
 void DebugCodegen::GenerateDebugBreakStub(MacroAssembler* masm,
                                           DebugBreakCallHelperMode mode) {
   __ RecordComment("Debug break");
 
   // Enter an internal frame.
   {
     FrameScope scope(masm, StackFrame::INTERNAL);
 
     // Load padding words on stack.
@@ skipping 68 matching lines @@
 }
 
 const bool LiveEdit::kFrameDropperSupported = true;
 
 #undef __
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_X64