[debugger] Use code offsets from frame summary in FromFrame Function.

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 131 matching lines @@
 
 // Find the break point at the supplied address, or the closest one before
 // the address.
 BreakLocation BreakLocation::FromCodeOffset(Handle<DebugInfo> debug_info,
                                             int offset) {
   Iterator it(debug_info, ALL_BREAK_LOCATIONS);
   it.SkipTo(BreakIndexFromCodeOffset(debug_info, offset));
   return it.GetBreakLocation();
 }
 
+// Put GetFirstFrameSummary Declaration here as FromFrame use it.
+FrameSummary GetFirstFrameSummary(JavaScriptFrame* frame);

[Yang, 2016/02/05 08:49:34]

Can you simply move the function definition to here?

 BreakLocation BreakLocation::FromFrame(Handle<DebugInfo> debug_info,
                                        JavaScriptFrame* frame) {
   // Code offset to the instruction after the current one, possibly a break
   // location as well. So the "- 1" to exclude it from the search.
-  Code* code = frame->LookupCode();
-  int code_offset = static_cast<int>(frame->pc() - code->instruction_start());
-  return FromCodeOffset(debug_info, code_offset - 1);
+  // Get code offset from the unoptimized code.
+  FrameSummary summary = GetFirstFrameSummary(frame);
+  Handle<JSFunction> function(summary.function());

[Yang, 2016/02/05 08:49:34]

You don't need to refresh the frame summary here. We only do that at other call
sites because we may not have the debug info, so we may have to recompile the
code. Here we already have the debug info.

+  Handle<SharedFunctionInfo> shared(function->shared());
+  // Refresh frame summary if the code has been recompiled for debugging.
+  if (AbstractCode::cast(shared->code()) != *summary.abstract_code()) {
+    summary = GetFirstFrameSummary(frame);
+  }
+
+  return FromCodeOffset(debug_info, summary.code_offset() - 1);
 }
 
 // Find the break point at the supplied address, or the closest one before
 // the address.
 void BreakLocation::FromCodeOffsetSameStatement(
     Handle<DebugInfo> debug_info, int offset, List<BreakLocation>* result_out) {
   int break_index = BreakIndexFromCodeOffset(debug_info, offset);
   Iterator it(debug_info, ALL_BREAK_LOCATIONS);
   it.SkipTo(break_index);
   int statement_position = it.statement_position();
@@ skipping 2291 matching lines @@
 }
 
 
 void LockingCommandMessageQueue::Clear() {
   base::LockGuard<base::Mutex> lock_guard(&mutex_);
   queue_.Clear();
 }
 
 }  // namespace internal
 }  // namespace v8