[debugger] separate break point info from code instrumentation.

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 <memory>
 
 #include "src/api.h"
 #include "src/arguments.h"
@@ skipping 15 matching lines @@
 #include "src/messages.h"
 #include "src/snapshot/natives.h"
 #include "src/wasm/wasm-debug.h"
 #include "src/wasm/wasm-module.h"
 
 #include "include/v8-debug.h"
 
 namespace v8 {
 namespace internal {
 
-namespace {
-
-inline int CallOffsetFromCodeOffset(int code_offset, bool is_interpreted) {
-  // Code offset points to the instruction after the call. Subtract 1 to
-  // exclude that instruction from the search. For bytecode, the code offset
-  // still points to the call.
-  return is_interpreted ? code_offset : code_offset - 1;
-}
-
-}  // namespace
-
 Debug::Debug(Isolate* isolate)
     : debug_context_(Handle<Context>()),
       event_listener_(Handle<Object>()),
       event_listener_data_(Handle<Object>()),
       message_handler_(NULL),
       command_received_(0),
       command_queue_(isolate->logger(), kQueueInitialSize),
       is_active_(false),
       is_suppressed_(false),
       live_edit_enabled_(true),  // TODO(yangguo): set to false by default.
       break_disabled_(false),
       break_points_active_(true),
       in_debug_event_listener_(false),
       break_on_exception_(false),
       break_on_uncaught_exception_(false),
       debug_info_list_(NULL),
       feature_tracker_(isolate),
       isolate_(isolate) {
   ThreadInit();
 }
 
-
-static v8::Local<v8::Context> GetDebugEventContext(Isolate* isolate) {
-  Handle<Context> context = isolate->debug()->debugger_entry()->GetContext();
-  // Isolate::context() may have been NULL when "script collected" event
-  // occured.
-  if (context.is_null()) return v8::Local<v8::Context>();
-  Handle<Context> native_context(context->native_context());
-  return v8::Utils::ToLocal(native_context);
+BreakLocation BreakLocation::FromFrame(Handle<DebugInfo> debug_info,
+                                       JavaScriptFrame* frame) {
+  FrameSummary summary = FrameSummary::GetFirst(frame);
+  int offset = summary.code_offset();
+  Handle<AbstractCode> abstract_code = summary.abstract_code();
+  if (abstract_code->IsCode()) offset = offset - 1;
+  auto it = BreakIterator::GetIterator(debug_info, abstract_code);
+  it->SkipTo(BreakIndexFromCodeOffset(debug_info, abstract_code, offset));
+  return it->GetBreakLocation();
 }
 
-BreakLocation::BreakLocation(Handle<DebugInfo> debug_info, DebugBreakType type,
-                             int code_offset, int position,
-                             int statement_position)
-    : debug_info_(debug_info),
-      code_offset_(code_offset),
-      type_(type),
-      position_(position),
-      statement_position_(statement_position) {}
-
-BreakLocation::Iterator* BreakLocation::GetIterator(
-    Handle<DebugInfo> debug_info, BreakLocatorType type) {
-  if (debug_info->abstract_code()->IsBytecodeArray()) {
-    return new BytecodeArrayIterator(debug_info, type);
-  } else {
-    return new CodeIterator(debug_info, type);
+void BreakLocation::AllAtCurrentStatement(Handle<DebugInfo> debug_info,
+                                          JavaScriptFrame* frame,
+                                          List<BreakLocation>* result_out) {
+  FrameSummary summary = FrameSummary::GetFirst(frame);
+  int offset = summary.code_offset();
+  Handle<AbstractCode> abstract_code = summary.abstract_code();
+  if (abstract_code->IsCode()) offset = offset - 1;
+  int statement_position;
+  {
+    auto it = BreakIterator::GetIterator(debug_info, abstract_code);
+    it->SkipTo(BreakIndexFromCodeOffset(debug_info, abstract_code, offset));
+    statement_position = it->statement_position();
+  }
+  for (auto it = BreakIterator::GetIterator(debug_info, abstract_code);
+       !it->Done(); it->Next()) {
+    if (it->statement_position() == statement_position) {
+      result_out->Add(it->GetBreakLocation());
+    }
   }
 }
 
-BreakLocation::Iterator::Iterator(Handle<DebugInfo> debug_info)
-    : debug_info_(debug_info), break_index_(-1) {
+int BreakLocation::BreakIndexFromCodeOffset(Handle<DebugInfo> debug_info,
+                                            Handle<AbstractCode> abstract_code,
+                                            int offset) {
+  // Run through all break points to locate the one closest to the address.
+  int closest_break = 0;
+  int distance = kMaxInt;
+  DCHECK(0 <= offset && offset < abstract_code->Size());
+  for (auto it = BreakIterator::GetIterator(debug_info, abstract_code);
+       !it->Done(); it->Next()) {
+    // Check if this break point is closer that what was previously found.
+    if (it->code_offset() <= offset && offset - it->code_offset() < distance) {
+      closest_break = it->break_index();
+      distance = offset - it->code_offset();
+      // Check whether we can't get any closer.
+      if (distance == 0) break;
+    }
+  }
+  return closest_break;
+}
+
+bool BreakLocation::HasBreakPoint(Handle<DebugInfo> debug_info) const {
+  // First check whether there is a break point with the same source position.
+  if (!debug_info->HasBreakPoint(position_)) return false;
+  // Then check whether a break point at that source position would have
+  // the same code offset. Otherwise it's just a break location that we can
+  // step to, but not actually a location where we can put a break point.
+  if (abstract_code_->IsCode()) {
+    CodeBreakIterator it(debug_info, ALL_BREAK_LOCATIONS);
+    it.SkipToPosition(position_, BREAK_POSITION_ALIGNED);
+    return it.code_offset() == code_offset_;
+  } else {

[jgruber, 2016/08/11 14:28:13]

Is abstract_code_->IsByteCodeArray() at this point? What about
debug_info->DebugCode() == abstract_code_ above?

Maybe we could add some DCHECKs in CodeBreakIterator/BytecodeArrayBreakIterator
constructors.

[Yang, 2016/08/12 05:33:46]

Done. Not sure what kind of DCHECKs you had in mind for the BreakIterators
though.

+    BytecodeArrayBreakIterator it(debug_info, ALL_BREAK_LOCATIONS);
+    it.SkipToPosition(position_, BREAK_POSITION_ALIGNED);
+    return it.code_offset() == code_offset_;
+  }
+}
+
+std::unique_ptr<BreakIterator> BreakIterator::GetIterator(
+    Handle<DebugInfo> debug_info, Handle<AbstractCode> abstract_code,
+    BreakLocatorType type) {
+  if (abstract_code->IsBytecodeArray()) {
+    DCHECK(debug_info->HasDebugBytecodeArray());
+    return std::unique_ptr<BreakIterator>(
+        new BytecodeArrayBreakIterator(debug_info, type));
+  } else {
+    DCHECK(abstract_code->IsCode());
+    DCHECK(debug_info->HasDebugCode());
+    return std::unique_ptr<BreakIterator>(
+        new CodeBreakIterator(debug_info, type));
+  }
+}
+
+BreakIterator::BreakIterator(Handle<DebugInfo> debug_info,
+                             BreakLocatorType type)
+    : debug_info_(debug_info), break_index_(-1), break_locator_type_(type) {
   position_ = debug_info->shared()->start_position();
   statement_position_ = position_;
 }
 
-BreakLocation::CodeIterator::CodeIterator(Handle<DebugInfo> debug_info,
-                                          BreakLocatorType type)
-    : Iterator(debug_info),
-      reloc_iterator_(debug_info->abstract_code()->GetCode(),
-                      GetModeMask(type)),
+int BreakIterator::BreakIndexFromPosition(int source_position,
+                                          BreakPositionAlignment alignment) {
+  int distance = kMaxInt;
+  int closest_break = break_index();
+  while (!Done()) {
+    int next_position;
+    if (alignment == STATEMENT_ALIGNED) {
+      next_position = statement_position();
+    } else {
+      DCHECK(alignment == BREAK_POSITION_ALIGNED);
+      next_position = position();
+    }
+    if (source_position <= next_position &&
+        next_position - source_position < distance) {
+      closest_break = break_index();
+      distance = next_position - source_position;
+      // Check whether we can't get any closer.
+      if (distance == 0) break;
+    }
+    Next();
+  }
+  return closest_break;
+}
+
+CodeBreakIterator::CodeBreakIterator(Handle<DebugInfo> debug_info,
+                                     BreakLocatorType type)
+    : BreakIterator(debug_info, type),
+      reloc_iterator_(debug_info->DebugCode(), GetModeMask(type)),
       source_position_iterator_(
-          debug_info->abstract_code()->GetCode()->source_position_table()) {
+          debug_info->DebugCode()->source_position_table()) {
   // There is at least one break location.
   DCHECK(!Done());
   Next();
 }
 
-int BreakLocation::CodeIterator::GetModeMask(BreakLocatorType type) {
+int CodeBreakIterator::GetModeMask(BreakLocatorType type) {
   int mask = 0;
   mask |= RelocInfo::ModeMask(RelocInfo::DEBUG_BREAK_SLOT_AT_RETURN);
   mask |= RelocInfo::ModeMask(RelocInfo::DEBUG_BREAK_SLOT_AT_CALL);
   if (isolate()->is_tail_call_elimination_enabled()) {
     mask |= RelocInfo::ModeMask(RelocInfo::DEBUG_BREAK_SLOT_AT_TAIL_CALL);
   }
   if (type == ALL_BREAK_LOCATIONS) {
     mask |= RelocInfo::ModeMask(RelocInfo::DEBUG_BREAK_SLOT_AT_POSITION);
     mask |= RelocInfo::ModeMask(RelocInfo::DEBUGGER_STATEMENT);
   }
   return mask;
 }
 
-void BreakLocation::CodeIterator::Next() {
+void CodeBreakIterator::Next() {
   DisallowHeapAllocation no_gc;
   DCHECK(!Done());
 
   // Iterate through reloc info stopping at each breakable code target.
   bool first = break_index_ == -1;
 
   if (!first) reloc_iterator_.next();
   first = false;
   if (Done()) return;
 
   int offset = code_offset();
   while (!source_position_iterator_.done() &&
          source_position_iterator_.code_offset() <= offset) {
     position_ = source_position_iterator_.source_position();
     if (source_position_iterator_.is_statement()) {
       statement_position_ = position_;
     }
     source_position_iterator_.Advance();
   }
 
   DCHECK(RelocInfo::IsDebugBreakSlot(rmode()) ||
          RelocInfo::IsDebuggerStatement(rmode()));
   break_index_++;
 }
 
-BreakLocation BreakLocation::CodeIterator::GetBreakLocation() {
-  DebugBreakType type;
+DebugBreakType CodeBreakIterator::GetDebugBreakType() {
   if (RelocInfo::IsDebugBreakSlotAtReturn(rmode())) {
-    type = DEBUG_BREAK_SLOT_AT_RETURN;
+    return DEBUG_BREAK_SLOT_AT_RETURN;
   } else if (RelocInfo::IsDebugBreakSlotAtCall(rmode())) {
-    type = DEBUG_BREAK_SLOT_AT_CALL;
+    return DEBUG_BREAK_SLOT_AT_CALL;
   } else if (RelocInfo::IsDebugBreakSlotAtTailCall(rmode())) {
-    type = isolate()->is_tail_call_elimination_enabled()
+    return isolate()->is_tail_call_elimination_enabled()
                ? DEBUG_BREAK_SLOT_AT_TAIL_CALL
                : DEBUG_BREAK_SLOT_AT_CALL;
   } else if (RelocInfo::IsDebuggerStatement(rmode())) {
-    type = DEBUGGER_STATEMENT;
+    return DEBUGGER_STATEMENT;
   } else if (RelocInfo::IsDebugBreakSlot(rmode())) {
-    type = DEBUG_BREAK_SLOT;
+    return DEBUG_BREAK_SLOT;
   } else {
-    type = NOT_DEBUG_BREAK;
+    return NOT_DEBUG_BREAK;
   }
-  return BreakLocation(debug_info_, type, code_offset(), position(),
-                       statement_position());
 }
 
-BreakLocation::BytecodeArrayIterator::BytecodeArrayIterator(
+void CodeBreakIterator::SkipToPosition(int position,
+                                       BreakPositionAlignment alignment) {
+  CodeBreakIterator it(debug_info_, break_locator_type_);
+  SkipTo(it.BreakIndexFromPosition(position, alignment));
+}
+
+void CodeBreakIterator::SetDebugBreak() {
+  DebugBreakType debug_break_type = GetDebugBreakType();
+  if (debug_break_type == DEBUGGER_STATEMENT) return;
+  DCHECK(debug_break_type >= DEBUG_BREAK_SLOT);
+  Builtins* builtins = isolate()->builtins();
+  Handle<Code> target = debug_break_type == DEBUG_BREAK_SLOT_AT_RETURN
+                            ? builtins->Return_DebugBreak()
+                            : builtins->Slot_DebugBreak();
+  DebugCodegen::PatchDebugBreakSlot(isolate(), rinfo()->pc(), target);
+}
+
+void CodeBreakIterator::ClearDebugBreak() {
+  DebugBreakType debug_break_type = GetDebugBreakType();
+  if (debug_break_type == DEBUGGER_STATEMENT) return;
+  DCHECK(debug_break_type >= DEBUG_BREAK_SLOT);
+  DebugCodegen::ClearDebugBreakSlot(isolate(), rinfo()->pc());
+}
+
+bool CodeBreakIterator::IsDebugBreak() {
+  DebugBreakType debug_break_type = GetDebugBreakType();
+  if (debug_break_type == DEBUGGER_STATEMENT) return false;
+  DCHECK(debug_break_type >= DEBUG_BREAK_SLOT);
+  return DebugCodegen::DebugBreakSlotIsPatched(rinfo()->pc());
+}
+
+BreakLocation CodeBreakIterator::GetBreakLocation() {
+  Handle<AbstractCode> code(AbstractCode::cast(debug_info_->DebugCode()));
+  return BreakLocation(code, GetDebugBreakType(), code_offset(), position_);
+}
+
+BytecodeArrayBreakIterator::BytecodeArrayBreakIterator(
     Handle<DebugInfo> debug_info, BreakLocatorType type)
-    : Iterator(debug_info),
-      source_position_iterator_(debug_info->abstract_code()
-                                    ->GetBytecodeArray()
-                                    ->source_position_table()),
-      break_locator_type_(type) {
+    : BreakIterator(debug_info, type),
+      source_position_iterator_(
+          debug_info->DebugBytecodeArray()->source_position_table()) {
   // There is at least one break location.
   DCHECK(!Done());
   Next();
 }
 
-void BreakLocation::BytecodeArrayIterator::Next() {
+void BytecodeArrayBreakIterator::Next() {
   DisallowHeapAllocation no_gc;
   DCHECK(!Done());
   bool first = break_index_ == -1;
   while (!Done()) {
     if (!first) source_position_iterator_.Advance();
     first = false;
     if (Done()) return;
     position_ = source_position_iterator_.source_position();
     if (source_position_iterator_.is_statement()) {
       statement_position_ = position_;
     }
     DCHECK(position_ >= 0);
     DCHECK(statement_position_ >= 0);
 
-    enum DebugBreakType type = GetDebugBreakType();
+    DebugBreakType type = GetDebugBreakType();
     if (type == NOT_DEBUG_BREAK) continue;
 
     if (break_locator_type_ == ALL_BREAK_LOCATIONS) break;
 
     DCHECK_EQ(CALLS_AND_RETURNS, break_locator_type_);
     if (type == DEBUG_BREAK_SLOT_AT_CALL) break;
     if (type == DEBUG_BREAK_SLOT_AT_RETURN) break;
   }
   break_index_++;
 }
 
-BreakLocation::DebugBreakType
-BreakLocation::BytecodeArrayIterator::GetDebugBreakType() {
-  BytecodeArray* bytecode_array = debug_info_->original_bytecode_array();
+DebugBreakType BytecodeArrayBreakIterator::GetDebugBreakType() {
+  BytecodeArray* bytecode_array = debug_info_->OriginalBytecodeArray();
   interpreter::Bytecode bytecode =
       interpreter::Bytecodes::FromByte(bytecode_array->get(code_offset()));
 
   if (bytecode == interpreter::Bytecode::kDebugger) {
     return DEBUGGER_STATEMENT;
   } else if (bytecode == interpreter::Bytecode::kReturn) {
     return DEBUG_BREAK_SLOT_AT_RETURN;
   } else if (bytecode == interpreter::Bytecode::kTailCall) {
     return isolate()->is_tail_call_elimination_enabled()
                ? DEBUG_BREAK_SLOT_AT_TAIL_CALL
                : DEBUG_BREAK_SLOT_AT_CALL;
   } else if (interpreter::Bytecodes::IsCallOrNew(bytecode)) {
     return DEBUG_BREAK_SLOT_AT_CALL;
   } else if (source_position_iterator_.is_statement()) {
     return DEBUG_BREAK_SLOT;
   } else {
     return NOT_DEBUG_BREAK;
   }
 }
 
-BreakLocation BreakLocation::BytecodeArrayIterator::GetBreakLocation() {
-  return BreakLocation(debug_info_, GetDebugBreakType(), code_offset(),
-                       position(), statement_position());
+void BytecodeArrayBreakIterator::SkipToPosition(
+    int position, BreakPositionAlignment alignment) {
+  BytecodeArrayBreakIterator it(debug_info_, break_locator_type_);
+  SkipTo(it.BreakIndexFromPosition(position, alignment));
 }
 
-// Find the break point at the supplied address, or the closest one before
-// the address.
-BreakLocation BreakLocation::FromCodeOffset(Handle<DebugInfo> debug_info,
-                                            int offset) {
-  std::unique_ptr<Iterator> it(GetIterator(debug_info));
-  it->SkipTo(BreakIndexFromCodeOffset(debug_info, offset));
-  return it->GetBreakLocation();
+void BytecodeArrayBreakIterator::SetDebugBreak() {
+  DebugBreakType debug_break_type = GetDebugBreakType();
+  if (debug_break_type == DEBUGGER_STATEMENT) return;
+  DCHECK(debug_break_type >= DEBUG_BREAK_SLOT);
+  BytecodeArray* bytecode_array = debug_info_->DebugBytecodeArray();
+  interpreter::Bytecode bytecode =
+      interpreter::Bytecodes::FromByte(bytecode_array->get(code_offset()));
+  if (interpreter::Bytecodes::IsDebugBreak(bytecode)) return;
+  interpreter::Bytecode debugbreak =
+      interpreter::Bytecodes::GetDebugBreak(bytecode);
+  bytecode_array->set(code_offset(),
+                      interpreter::Bytecodes::ToByte(debugbreak));
 }
 
-BreakLocation BreakLocation::FromFrame(Handle<DebugInfo> debug_info,
-                                       JavaScriptFrame* frame) {
-  int code_offset = FrameSummary::GetFirst(frame).code_offset();
-  int call_offset =
-      CallOffsetFromCodeOffset(code_offset, frame->is_interpreted());
-  return FromCodeOffset(debug_info, call_offset);
+void BytecodeArrayBreakIterator::ClearDebugBreak() {
+  DebugBreakType debug_break_type = GetDebugBreakType();
+  if (debug_break_type == DEBUGGER_STATEMENT) return;
+  DCHECK(debug_break_type >= DEBUG_BREAK_SLOT);
+  BytecodeArray* bytecode_array = debug_info_->DebugBytecodeArray();
+  BytecodeArray* original = debug_info_->OriginalBytecodeArray();
+  bytecode_array->set(code_offset(), original->get(code_offset()));
 }
 
-void BreakLocation::AllForStatementPosition(Handle<DebugInfo> debug_info,
-                                            int statement_position,
-                                            List<BreakLocation>* result_out) {
-  for (std::unique_ptr<Iterator> it(GetIterator(debug_info)); !it->Done();
-       it->Next()) {
-    if (it->statement_position() == statement_position) {
-      result_out->Add(it->GetBreakLocation());
-    }
-  }
+bool BytecodeArrayBreakIterator::IsDebugBreak() {
+  DebugBreakType debug_break_type = GetDebugBreakType();
+  if (debug_break_type == DEBUGGER_STATEMENT) return false;
+  DCHECK(debug_break_type >= DEBUG_BREAK_SLOT);
+  BytecodeArray* bytecode_array = debug_info_->DebugBytecodeArray();
+  interpreter::Bytecode bytecode =
+      interpreter::Bytecodes::FromByte(bytecode_array->get(code_offset()));
+  return interpreter::Bytecodes::IsDebugBreak(bytecode);
 }
 
-int BreakLocation::BreakIndexFromCodeOffset(Handle<DebugInfo> debug_info,
-                                            int offset) {
-  // Run through all break points to locate the one closest to the address.
-  int closest_break = 0;
-  int distance = kMaxInt;
-  DCHECK(0 <= offset && offset < debug_info->abstract_code()->Size());
-  for (std::unique_ptr<Iterator> it(GetIterator(debug_info)); !it->Done();
-       it->Next()) {
-    // Check if this break point is closer that what was previously found.
-    if (it->code_offset() <= offset && offset - it->code_offset() < distance) {
-      closest_break = it->break_index();
-      distance = offset - it->code_offset();
-      // Check whether we can't get any closer.
-      if (distance == 0) break;
-    }
-  }
-  return closest_break;
+BreakLocation BytecodeArrayBreakIterator::GetBreakLocation() {
+  Handle<AbstractCode> code(
+      AbstractCode::cast(debug_info_->DebugBytecodeArray()));
+  return BreakLocation(code, GetDebugBreakType(), code_offset(), position_);
 }
 
 
-BreakLocation BreakLocation::FromPosition(Handle<DebugInfo> debug_info,
-                                          int position,
-                                          BreakPositionAlignment alignment) {
-  // Run through all break points to locate the one closest to the source
-  // position.
-  int distance = kMaxInt;
-  std::unique_ptr<Iterator> it(GetIterator(debug_info));
-  BreakLocation closest_break = it->GetBreakLocation();
-  while (!it->Done()) {
-    int next_position;
-    if (alignment == STATEMENT_ALIGNED) {
-      next_position = it->statement_position();
-    } else {
-      DCHECK(alignment == BREAK_POSITION_ALIGNED);
-      next_position = it->position();
-    }
-    if (position <= next_position && next_position - position < distance) {
-      closest_break = it->GetBreakLocation();
-      distance = next_position - position;
-      // Check whether we can't get any closer.
-      if (distance == 0) break;
-    }
-    it->Next();
-  }
-  return closest_break;
-}
-
-
-void BreakLocation::SetBreakPoint(Handle<Object> break_point_object) {
-  // If there is not already a real break point here patch code with debug
-  // break.
-  if (!HasBreakPoint()) SetDebugBreak();
-  DCHECK(IsDebugBreak() || IsDebuggerStatement());
-  // Set the break point information.
-  DebugInfo::SetBreakPoint(debug_info_, position_, statement_position_,
-                           break_point_object);
-}
-
-
-void BreakLocation::ClearBreakPoint(Handle<Object> break_point_object) {
-  // Clear the break point information.
-  DebugInfo::ClearBreakPoint(debug_info_, position_, break_point_object);
-  // If there are no more break points here remove the debug break.
-  if (!HasBreakPoint()) {
-    ClearDebugBreak();
-    DCHECK(!IsDebugBreak());
-  }
-}
-
-
-void BreakLocation::SetOneShot() {
-  // Debugger statement always calls debugger. No need to modify it.
-  if (IsDebuggerStatement()) return;
-
-  // Patch code with debug break.
-  SetDebugBreak();
-}
-
-
-void BreakLocation::ClearOneShot() {
-  // Debugger statement always calls debugger. No need to modify it.
-  if (IsDebuggerStatement()) return;
-
-  // If there is a real break point here no more to do.
-  if (HasBreakPoint()) {
-    DCHECK(IsDebugBreak());
-    return;
-  }
-
-  // Patch code removing debug break.
-  ClearDebugBreak();
-  DCHECK(!IsDebugBreak());
-}
-
-
-void BreakLocation::SetDebugBreak() {
-  // Debugger statement always calls debugger. No need to modify it.
-  if (IsDebuggerStatement()) return;
-
-  // If there is already a break point here just return. This might happen if
-  // the same code is flooded with break points twice. Flooding the same
-  // function twice might happen when stepping in a function with an exception
-  // handler as the handler and the function is the same.
-  if (IsDebugBreak()) return;
-
-  DCHECK(IsDebugBreakSlot());
-  if (abstract_code()->IsCode()) {
-    Code* code = abstract_code()->GetCode();
-    DCHECK(code->kind() == Code::FUNCTION);
-    Builtins* builtins = isolate()->builtins();
-    Handle<Code> target = IsReturn() ? builtins->Return_DebugBreak()
-                                     : builtins->Slot_DebugBreak();
-    Address pc = code->instruction_start() + code_offset();
-    DebugCodegen::PatchDebugBreakSlot(isolate(), pc, target);
-  } else {
-    BytecodeArray* bytecode_array = abstract_code()->GetBytecodeArray();
-    interpreter::Bytecode bytecode =
-        interpreter::Bytecodes::FromByte(bytecode_array->get(code_offset()));
-    interpreter::Bytecode debugbreak =
-        interpreter::Bytecodes::GetDebugBreak(bytecode);
-    bytecode_array->set(code_offset(),
-                        interpreter::Bytecodes::ToByte(debugbreak));
-  }
-  DCHECK(IsDebugBreak());
-}
-
-
-void BreakLocation::ClearDebugBreak() {
-  // Debugger statement always calls debugger. No need to modify it.
-  if (IsDebuggerStatement()) return;
-
-  DCHECK(IsDebugBreakSlot());
-  if (abstract_code()->IsCode()) {
-    Code* code = abstract_code()->GetCode();
-    DCHECK(code->kind() == Code::FUNCTION);
-    Address pc = code->instruction_start() + code_offset();
-    DebugCodegen::ClearDebugBreakSlot(isolate(), pc);
-  } else {
-    BytecodeArray* bytecode_array = abstract_code()->GetBytecodeArray();
-    BytecodeArray* original = debug_info_->original_bytecode_array();
-    bytecode_array->set(code_offset(), original->get(code_offset()));
-  }
-  DCHECK(!IsDebugBreak());
-}
-
-
-bool BreakLocation::IsDebugBreak() const {
-  if (IsDebuggerStatement()) return false;
-  DCHECK(IsDebugBreakSlot());
-  if (abstract_code()->IsCode()) {
-    Code* code = abstract_code()->GetCode();
-    DCHECK(code->kind() == Code::FUNCTION);
-    Address pc = code->instruction_start() + code_offset();
-    return DebugCodegen::DebugBreakSlotIsPatched(pc);
-  } else {
-    BytecodeArray* bytecode_array = abstract_code()->GetBytecodeArray();
-    interpreter::Bytecode bytecode =
-        interpreter::Bytecodes::FromByte(bytecode_array->get(code_offset()));
-    return interpreter::Bytecodes::IsDebugBreak(bytecode);
-  }
-}
-
-Handle<Object> BreakLocation::BreakPointObjects() const {
-  return debug_info_->GetBreakPointObjects(position_);
-}
-
-bool BreakLocation::HasBreakPoint() const {
-  // First check whether there is a break point with the same source position.
-  if (!debug_info_->HasBreakPoint(position_)) return false;
-  // Then check whether a break point at that source position would have
-  // the same code offset. Otherwise it's just a break location that we can
-  // step to, but not actually a location where we can put a break point.
-  BreakLocation break_point_location = BreakLocation::FromPosition(
-      debug_info_, position_, BREAK_POSITION_ALIGNED);
-  return break_point_location.code_offset() == code_offset_;
-}
-
 void DebugFeatureTracker::Track(DebugFeatureTracker::Feature feature) {
   uint32_t mask = 1 << feature;
   // Only count one sample per feature and isolate.
   if (bitfield_ & mask) return;
   isolate_->counters()->debug_feature_usage()->AddSample(feature);
   bitfield_ |= mask;
 }
 
 
 // Threading support.
@@ skipping 118 matching lines @@
   if (!EnsureDebugInfo(shared, function)) {
     // Return if we failed to retrieve the debug info.
     return;
   }
   Handle<DebugInfo> debug_info(shared->GetDebugInfo(), isolate_);
 
   // Find the break location where execution has stopped.
   BreakLocation location = BreakLocation::FromFrame(debug_info, frame);
 
   // Find actual break points, if any, and trigger debug break event.
-  Handle<Object> break_points_hit = CheckBreakPoints(&location);
+  Handle<Object> break_points_hit = CheckBreakPoints(debug_info, &location);
   if (!break_points_hit->IsUndefined(isolate_)) {
     // Clear all current stepping setup.
     ClearStepping();
     // Notify the debug event listeners.
     OnDebugBreak(break_points_hit, false);
     return;
   }
 
   // No break point. Check for stepping.
   StepAction step_action = last_step_action();
@@ skipping 15 matching lines @@
       if (current_fp < target_fp) return;
       // For step-next, a tail call is like a return and should break.
       step_break = location.IsTailCall();
     // Fall through.
     case StepIn: {
       FrameSummary summary = FrameSummary::GetFirst(frame);
       int offset = summary.code_offset();
       step_break = step_break || location.IsReturn() ||
                    (current_fp != last_fp) ||
                    (thread_local_.last_statement_position_ !=
-                    location.abstract_code()->SourceStatementPosition(offset));
+                    summary.abstract_code()->SourceStatementPosition(offset));
       break;
     }
     case StepFrame:
       step_break = current_fp != last_fp;
       break;
   }
 
   // Clear all current stepping setup.
   ClearStepping();
 
   if (step_break) {
     // Notify the debug event listeners.
     OnDebugBreak(isolate_->factory()->undefined_value(), false);
   } else {
     // Re-prepare to continue.
     PrepareStep(step_action);
   }
 }
 
 
 // Find break point objects for this location, if any, and evaluate them.
 // Return an array of break point objects that evaluated true.
-Handle<Object> Debug::CheckBreakPoints(BreakLocation* location,
+Handle<Object> Debug::CheckBreakPoints(Handle<DebugInfo> debug_info,
+                                       BreakLocation* location,
                                        bool* has_break_points) {
   Factory* factory = isolate_->factory();
   bool has_break_points_to_check =
-      break_points_active_ && location->HasBreakPoint();
+      break_points_active_ && location->HasBreakPoint(debug_info);
   if (has_break_points) *has_break_points = has_break_points_to_check;
   if (!has_break_points_to_check) return factory->undefined_value();
 
-  Handle<Object> break_point_objects = location->BreakPointObjects();
+  Handle<Object> break_point_objects =
+      debug_info->GetBreakPointObjects(location->position());
   // Count the number of break points hit. If there are multiple break points
   // they are in a FixedArray.
   Handle<FixedArray> break_points_hit;
   int break_points_hit_count = 0;
   DCHECK(!break_point_objects->IsUndefined(isolate_));
   if (break_point_objects->IsFixedArray()) {
     Handle<FixedArray> array(FixedArray::cast(*break_point_objects));
     break_points_hit = factory->NewFixedArray(array->length());
     for (int i = 0; i < array->length(); i++) {
       Handle<Object> break_point_object(array->get(i), isolate_);
@@ skipping 22 matching lines @@
   // an exception event on exception at this location.
   Object* fun = frame->function();
   if (!fun->IsJSFunction()) return false;
   JSFunction* function = JSFunction::cast(fun);
   if (!function->shared()->HasDebugInfo()) return false;
   HandleScope scope(isolate_);
   Handle<DebugInfo> debug_info(function->shared()->GetDebugInfo());
   // Enter the debugger.
   DebugScope debug_scope(this);
   if (debug_scope.failed()) return false;
-  BreakLocation current_position = BreakLocation::FromFrame(debug_info, frame);
   List<BreakLocation> break_locations;
-  BreakLocation::AllForStatementPosition(
-      debug_info, current_position.statement_position(), &break_locations);
+  BreakLocation::AllAtCurrentStatement(debug_info, frame, &break_locations);
   bool has_break_points_at_all = false;
   for (int i = 0; i < break_locations.length(); i++) {
     bool has_break_points;
     Handle<Object> check_result =
-        CheckBreakPoints(&break_locations[i], &has_break_points);
+        CheckBreakPoints(debug_info, &break_locations[i], &has_break_points);
     has_break_points_at_all |= has_break_points;
     if (has_break_points && !check_result->IsUndefined(isolate_)) return false;
   }
   return has_break_points_at_all;
 }
 
 
 MaybeHandle<Object> Debug::CallFunction(const char* name, int argc,
                                         Handle<Object> args[]) {
   PostponeInterruptsScope no_interrupts(isolate_);
@@ skipping 41 matching lines @@
   if (!EnsureDebugInfo(shared, function)) {
     // Return if retrieving debug info failed.
     return true;
   }
 
   Handle<DebugInfo> debug_info(shared->GetDebugInfo());
   // Source positions starts with zero.
   DCHECK(*source_position >= 0);
 
   // Find the break point and change it.
-  BreakLocation location = BreakLocation::FromPosition(
-      debug_info, *source_position, STATEMENT_ALIGNED);
-  *source_position = location.statement_position();
-  location.SetBreakPoint(break_point_object);
+  *source_position =
+      FindBreakablePosition(debug_info, *source_position, STATEMENT_ALIGNED);
+  DebugInfo::SetBreakPoint(debug_info, *source_position, break_point_object);
+  // At least one active break point now.
+  DCHECK(debug_info->GetBreakPointCount() > 0);
+
+  ClearBreakPoints(debug_info);
+  ApplyBreakPoints(debug_info);
 
   feature_tracker()->Track(DebugFeatureTracker::kBreakPoint);
-
-  // At least one active break point now.
-  return debug_info->GetBreakPointCount() > 0;
+  return true;
 }
 
 
 bool Debug::SetBreakPointForScript(Handle<Script> script,
                                    Handle<Object> break_point_object,
                                    int* source_position,
                                    BreakPositionAlignment alignment) {
   if (script->type() == Script::TYPE_WASM) {
     // TODO(clemensh): set breakpoint for wasm.
     return false;
@@ skipping 14 matching lines @@
 
   // Find position within function. The script position might be before the
   // source position of the first function.
   if (shared->start_position() > *source_position) {
     *source_position = shared->start_position();
   }
 
   Handle<DebugInfo> debug_info(shared->GetDebugInfo());
 
   // Find the break point and change it.
-  BreakLocation location =
-      BreakLocation::FromPosition(debug_info, *source_position, alignment);
-  location.SetBreakPoint(break_point_object);
+  *source_position =
+      FindBreakablePosition(debug_info, *source_position, alignment);
+  DebugInfo::SetBreakPoint(debug_info, *source_position, break_point_object);
+  // At least one active break point now.
+  DCHECK(debug_info->GetBreakPointCount() > 0);
+
+  ClearBreakPoints(debug_info);
+  ApplyBreakPoints(debug_info);
 
   feature_tracker()->Track(DebugFeatureTracker::kBreakPoint);
-
-  *source_position = (alignment == STATEMENT_ALIGNED)
-                         ? location.statement_position()
-                         : location.position();
-
-  // At least one active break point now.
-  DCHECK(debug_info->GetBreakPointCount() > 0);
   return true;
 }
 
+int Debug::FindBreakablePosition(Handle<DebugInfo> debug_info,
+                                 int source_position,
+                                 BreakPositionAlignment alignment) {
+  int statement_position;
+  int position;
+  if (debug_info->HasDebugCode()) {
+    CodeBreakIterator it(debug_info, ALL_BREAK_LOCATIONS);
+    it.SkipToPosition(source_position, alignment);
+    statement_position = it.statement_position();
+    position = it.position();
+  } else {
+    DCHECK(debug_info->HasDebugBytecodeArray());
+    BytecodeArrayBreakIterator it(debug_info, ALL_BREAK_LOCATIONS);
+    it.SkipToPosition(source_position, alignment);
+    statement_position = it.statement_position();
+    position = it.position();
+  }
+  return alignment == STATEMENT_ALIGNED ? statement_position : position;
+}
+
+void Debug::ApplyBreakPoints(Handle<DebugInfo> debug_info) {
+  DisallowHeapAllocation no_gc;
+  if (debug_info->break_points()->IsUndefined(isolate_)) return;
+  FixedArray* break_points = debug_info->break_points();
+  for (int i = 0; i < break_points->length(); i++) {
+    if (break_points->get(i)->IsUndefined(isolate_)) continue;
+    BreakPointInfo* info = BreakPointInfo::cast(break_points->get(i));
+    if (info->GetBreakPointCount() == 0) continue;
+    if (debug_info->HasDebugCode()) {
+      CodeBreakIterator it(debug_info, ALL_BREAK_LOCATIONS);
+      it.SkipToPosition(info->source_position(), BREAK_POSITION_ALIGNED);
+      it.SetDebugBreak();
+    }
+    if (debug_info->HasDebugBytecodeArray()) {
+      BytecodeArrayBreakIterator it(debug_info, ALL_BREAK_LOCATIONS);
+      it.SkipToPosition(info->source_position(), BREAK_POSITION_ALIGNED);
+      it.SetDebugBreak();
+    }
+  }
+}
+
+void Debug::ClearBreakPoints(Handle<DebugInfo> debug_info) {
+  DisallowHeapAllocation no_gc;
+  if (debug_info->HasDebugCode()) {
+    for (CodeBreakIterator it(debug_info, ALL_BREAK_LOCATIONS); !it.Done();
+         it.Next()) {
+      it.ClearDebugBreak();
+    }
+  }
+  if (debug_info->HasDebugBytecodeArray()) {
+    for (BytecodeArrayBreakIterator it(debug_info, ALL_BREAK_LOCATIONS);
+         !it.Done(); it.Next()) {
+      it.ClearDebugBreak();
+    }
+  }
+}
 
 void Debug::ClearBreakPoint(Handle<Object> break_point_object) {
   HandleScope scope(isolate_);
 
-  DebugInfoListNode* node = debug_info_list_;
-  while (node != NULL) {
+  for (DebugInfoListNode* node = debug_info_list_; node != NULL;
+       node = node->next()) {
     Handle<Object> result =
         DebugInfo::FindBreakPointInfo(node->debug_info(), break_point_object);
-    if (!result->IsUndefined(isolate_)) {
-      // Get information in the break point.
-      Handle<BreakPointInfo> break_point_info =
-          Handle<BreakPointInfo>::cast(result);
-      Handle<DebugInfo> debug_info = node->debug_info();
-
-      BreakLocation location = BreakLocation::FromPosition(
-          debug_info, break_point_info->source_position(),
-          BREAK_POSITION_ALIGNED);
-      location.ClearBreakPoint(break_point_object);
-
-      // If there are no more break points left remove the debug info for this
-      // function.
+    if (result->IsUndefined(isolate_)) continue;
+    Handle<DebugInfo> debug_info = node->debug_info();
+    if (DebugInfo::ClearBreakPoint(debug_info, break_point_object)) {
+      ClearBreakPoints(debug_info);
       if (debug_info->GetBreakPointCount() == 0) {
         RemoveDebugInfoAndClearFromShared(debug_info);
+      } else {
+        ApplyBreakPoints(debug_info);
       }
-
       return;
     }
-    node = node->next();
   }
 }
 
-
 // Clear out all the debug break code. This is ONLY supposed to be used when
 // shutting down the debugger as it will leave the break point information in
 // DebugInfo even though the code is patched back to the non break point state.
 void Debug::ClearAllBreakPoints() {
   for (DebugInfoListNode* node = debug_info_list_; node != NULL;
        node = node->next()) {
-    for (std::unique_ptr<BreakLocation::Iterator> it(
-             BreakLocation::GetIterator(node->debug_info()));
-         !it->Done(); it->Next()) {
-      it->GetBreakLocation().ClearDebugBreak();
-    }
+    ClearBreakPoints(node->debug_info());
   }
   // Remove all debug info.
   while (debug_info_list_ != NULL) {
     RemoveDebugInfoAndClearFromShared(debug_info_list_->debug_info());
   }
 }
 
-
 void Debug::FloodWithOneShot(Handle<JSFunction> function,
                              BreakLocatorType type) {
   // Debug utility functions are not subject to debugging.
   if (function->native_context() == *debug_context()) return;
 
   if (!function->shared()->IsSubjectToDebugging()) {
     // Builtin functions are not subject to stepping, but need to be
     // deoptimized, because optimized code does not check for debug
     // step in at call sites.
     Deoptimizer::DeoptimizeFunction(*function);
     return;
   }
   // Make sure the function is compiled and has set up the debug info.
   Handle<SharedFunctionInfo> shared(function->shared());
   if (!EnsureDebugInfo(shared, function)) {
     // Return if we failed to retrieve the debug info.
     return;
   }
 
   // Flood the function with break points.
   Handle<DebugInfo> debug_info(shared->GetDebugInfo());
-  for (std::unique_ptr<BreakLocation::Iterator> it(
-           BreakLocation::GetIterator(debug_info, type));
-       !it->Done(); it->Next()) {
-    it->GetBreakLocation().SetOneShot();
+  if (debug_info->HasDebugCode()) {
+    for (CodeBreakIterator it(debug_info, type); !it.Done(); it.Next()) {
+      it.SetDebugBreak();
+    }
+  }
+  if (debug_info->HasDebugBytecodeArray()) {
+    for (BytecodeArrayBreakIterator it(debug_info, type); !it.Done();
+         it.Next()) {
+      it.SetDebugBreak();
+    }
   }
 }
 
-
 void Debug::ChangeBreakOnException(ExceptionBreakType type, bool enable) {
   if (type == BreakUncaughtException) {
     break_on_uncaught_exception_ = enable;
   } else {
     break_on_exception_ = enable;
   }
 }
 
 
 bool Debug::IsBreakOnException(ExceptionBreakType type) {
@@ skipping 94 matching lines @@
   // Get the debug info (create it if it does not exist).
   FrameSummary summary = FrameSummary::GetFirst(frame);
   Handle<JSFunction> function(summary.function());
   Handle<SharedFunctionInfo> shared(function->shared());
   if (!EnsureDebugInfo(shared, function)) {
     // Return if ensuring debug info failed.
     return;
   }
 
   Handle<DebugInfo> debug_info(shared->GetDebugInfo());
-  // Refresh frame summary if the code has been recompiled for debugging.
-  if (AbstractCode::cast(shared->code()) != *summary.abstract_code()) {
-    summary = FrameSummary::GetFirst(frame);
-  }
-
-  int call_offset =
-      CallOffsetFromCodeOffset(summary.code_offset(), frame->is_interpreted());
-  BreakLocation location =
-      BreakLocation::FromCodeOffset(debug_info, call_offset);
+  BreakLocation location = BreakLocation::FromFrame(debug_info, frame);
 
   // Any step at a return is a step-out.
   if (location.IsReturn()) step_action = StepOut;
   // A step-next at a tail call is a step-out.
   if (location.IsTailCall() && step_action == StepNext) step_action = StepOut;
 
   thread_local_.last_statement_position_ =
-      debug_info->abstract_code()->SourceStatementPosition(
-          summary.code_offset());
+      summary.abstract_code()->SourceStatementPosition(summary.code_offset());
   thread_local_.last_fp_ = frame->UnpaddedFP();
   // No longer perform the current async step.
   clear_suspended_generator();
 
   switch (step_action) {
     case StepNone:
       UNREACHABLE();
       break;
     case StepOut:
       // Advance to caller frame.
@@ skipping 24 matching lines @@
       FloodWithOneShot(function);
       break;
     case StepFrame:
       // No point in setting one-shot breaks at places where we are not about
       // to leave the current frame.
       FloodWithOneShot(function, CALLS_AND_RETURNS);
       break;
   }
 }
 
-
 // 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();
   if (!shared->HasDebugInfo()) {
     return isolate->factory()->undefined_value();
   }
   Handle<DebugInfo> debug_info(shared->GetDebugInfo());
   if (debug_info->GetBreakPointCount() == 0) {
     return isolate->factory()->undefined_value();
   }
   Handle<FixedArray> locations =
       isolate->factory()->NewFixedArray(debug_info->GetBreakPointCount());
   int count = 0;
   for (int i = 0; i < debug_info->break_points()->length(); ++i) {
     if (!debug_info->break_points()->get(i)->IsUndefined(isolate)) {
       BreakPointInfo* break_point_info =
           BreakPointInfo::cast(debug_info->break_points()->get(i));
       int break_points = break_point_info->GetBreakPointCount();
       if (break_points == 0) continue;
       Smi* position = NULL;
       if (position_alignment == STATEMENT_ALIGNED) {
-        BreakLocation break_point_location = BreakLocation::FromPosition(
-            debug_info, break_point_info->source_position(),
-            BREAK_POSITION_ALIGNED);
-        position = Smi::FromInt(break_point_location.statement_position());
+        if (debug_info->HasDebugCode()) {
+          CodeBreakIterator it(debug_info, ALL_BREAK_LOCATIONS);
+          it.SkipToPosition(break_point_info->source_position(),
+                            BREAK_POSITION_ALIGNED);
+          position = Smi::FromInt(it.statement_position());
+        } else {

[jgruber, 2016/08/11 14:28:13]

Same here.

[Yang, 2016/08/12 05:33:46]

Done.

+          BytecodeArrayBreakIterator it(debug_info, ALL_BREAK_LOCATIONS);
+          it.SkipToPosition(break_point_info->source_position(),
+                            BREAK_POSITION_ALIGNED);
+          position = Smi::FromInt(it.statement_position());
+        }
       } else {
         DCHECK_EQ(BREAK_POSITION_ALIGNED, position_alignment);
         position = Smi::FromInt(break_point_info->source_position());
       }
       for (int j = 0; j < break_points; ++j) locations->set(count++, position);
     }
   }
   return locations;
 }
 
-
 void Debug::ClearStepping() {
   // Clear the various stepping setup.
   ClearOneShot();
 
   thread_local_.last_step_action_ = StepNone;
   thread_local_.last_statement_position_ = kNoSourcePosition;
   thread_local_.last_fp_ = 0;
   thread_local_.target_fp_ = 0;
 }
 
 
 // Clears all the one-shot break points that are currently set. Normally this
 // function is called each time a break point is hit as one shot break points
 // are used to support stepping.
 void Debug::ClearOneShot() {
   // The current implementation just runs through all the breakpoints. When the
   // last break point for a function is removed that function is automatically
   // removed from the list.
   for (DebugInfoListNode* node = debug_info_list_; node != NULL;
        node = node->next()) {
-    for (std::unique_ptr<BreakLocation::Iterator> it(
-             BreakLocation::GetIterator(node->debug_info()));
-         !it->Done(); it->Next()) {
-      it->GetBreakLocation().ClearOneShot();
-    }
+    Handle<DebugInfo> debug_info = node->debug_info();
+    ClearBreakPoints(debug_info);
+    ApplyBreakPoints(debug_info);

[jgruber, 2016/08/11 14:28:13]

Why are breakpoints reapplied here?

[Yang, 2016/08/12 05:33:46]

Because having a function flooded with one-shots means that we patch every break
location to break. When we clear these one-shots, we still want to break at
actual break points. So to clear one-shots, we clear all break locations, and
then re-apply break points.

   }
 }
 
 
 bool MatchingCodeTargets(Code* target1, Code* target2) {
   if (target1 == target2) return true;
   if (target1->kind() != target2->kind()) return false;
   return target1->is_handler() || target1->is_inline_cache_stub();
 }
 
@@ skipping 83 matching lines @@
     for (JavaScriptFrameIterator it(isolate, top); !it.done(); it.Advance()) {
       JavaScriptFrame* frame = it.frame();
       JSFunction* function = frame->function();
       if (frame->is_optimized()) continue;
       if (!function->Inlines(shared_)) continue;
 
       if (frame->is_interpreted()) {
         InterpretedFrame* interpreted_frame =
             reinterpret_cast<InterpretedFrame*>(frame);
         BytecodeArray* debug_copy =
-            shared_->GetDebugInfo()->abstract_code()->GetBytecodeArray();
+            shared_->GetDebugInfo()->DebugBytecodeArray();
         interpreted_frame->PatchBytecodeArray(debug_copy);
         continue;
       }
 
       Code* frame_code = frame->LookupCode();
       DCHECK(frame_code->kind() == Code::FUNCTION);
       if (frame_code->has_debug_break_slots()) continue;
 
       Code* new_code = function->shared()->code();
       Address old_pc = frame->pc();
@@ skipping 332 matching lines @@
 bool Debug::IsBreakAtReturn(JavaScriptFrame* frame) {
   HandleScope scope(isolate_);
 
   // Get the executing function in which the debug break occurred.
   Handle<SharedFunctionInfo> shared(frame->function()->shared());
 
   // With no debug info there are no break points, so we can't be at a return.
   if (!shared->HasDebugInfo()) return false;
 
   DCHECK(!frame->is_optimized());
-  int code_offset = FrameSummary::GetFirst(frame).code_offset();
   Handle<DebugInfo> debug_info(shared->GetDebugInfo());
-  BreakLocation location =
-      BreakLocation::FromCodeOffset(debug_info, code_offset);
+  BreakLocation location = BreakLocation::FromFrame(debug_info, frame);
   return location.IsReturn() || location.IsTailCall();
 }
 
 
 void Debug::FramesHaveBeenDropped(StackFrame::Id new_break_frame_id,
                                   LiveEdit::FrameDropMode mode) {
   if (mode != LiveEdit::CURRENTLY_SET_MODE) {
     thread_local_.frame_drop_mode_ = mode;
   }
   thread_local_.break_frame_id_ = new_break_frame_id;
@@ skipping 810 matching lines @@
     Handle<Object> json;
     if (!maybe_json.ToHandle(&json) || !json->IsString()) {
       return v8::Local<v8::String>();
     }
     return scope.Escape(v8::Utils::ToLocal(Handle<String>::cast(json)));
   } else {
     return v8::Utils::ToLocal(response_json_);
   }
 }
 
+namespace {
+v8::Local<v8::Context> GetDebugEventContext(Isolate* isolate) {
+  Handle<Context> context = isolate->debug()->debugger_entry()->GetContext();
+  // Isolate::context() may have been NULL when "script collected" event
+  // occured.
+  if (context.is_null()) return v8::Local<v8::Context>();
+  Handle<Context> native_context(context->native_context());
+  return v8::Utils::ToLocal(native_context);
+}
+}  // anonymous namespace
 
 v8::Local<v8::Context> MessageImpl::GetEventContext() const {
   Isolate* isolate = event_data_->GetIsolate();
   v8::Local<v8::Context> context = GetDebugEventContext(isolate);
   // Isolate::context() may be NULL when "script collected" event occurs.
   DCHECK(!context.IsEmpty());
   return context;
 }
 
 
@@ skipping 140 matching lines @@
 }
 
 
 void LockingCommandMessageQueue::Clear() {
   base::LockGuard<base::Mutex> lock_guard(&mutex_);
   queue_.Clear();
 }
 
 }  // namespace internal
 }  // namespace v8