[debugger] introduce abstract interface for break location.

src/debug/arm/debug-arm.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_ARM
 
 #include "src/codegen.h"
 #include "src/debug/debug.h"
 
 namespace v8 {
@@ skipping 44 matching lines @@
   //   skip:
   //   blx ip
   Label skip_constant;
   patcher.masm()->ldr(ip, MemOperand(v8::internal::pc, 0));
   patcher.masm()->b(&skip_constant);
   patcher.Emit(code->entry());
   patcher.masm()->bind(&skip_constant);
   patcher.masm()->blx(ip);
 }
 
+bool DebugCodegen::DebugBreakSlotIsPatched(Address pc) {
+  Instr current_instr = Assembler::instr_at(pc);
+  return !Assembler::IsNop(current_instr, Assembler::DEBUG_BREAK_NOP);
+}
 
 void DebugCodegen::GenerateDebugBreakStub(MacroAssembler* masm,
                                           DebugBreakCallHelperMode mode) {
   __ RecordComment("Debug break");
   {
     FrameAndConstantPoolScope scope(masm, StackFrame::INTERNAL);
 
     // Load padding words on stack.
     __ mov(ip, Operand(Smi::FromInt(LiveEdit::kFramePaddingValue)));
     for (int i = 0; i < LiveEdit::kFramePaddingInitialSize; i++) {
@@ skipping 69 matching lines @@
 
 
 const bool LiveEdit::kFrameDropperSupported = true;
 
 #undef __
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_ARM