Fix very strange bug in FindBreakLocationFromAddress algorithm

src/runtime.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 11211 matching lines @@
     // Get the debug info (create it if it does not exist).
     if (!isolate->debug()->EnsureDebugInfo(shared_info, function_)) {
       // Return if ensuring debug info failed.
       return;
     }
     Handle<DebugInfo> debug_info = Debug::GetDebugInfo(shared_info);
 
     // Find the break point where execution has stopped.
     BreakLocationIterator break_location_iterator(debug_info,
                                                   ALL_BREAK_LOCATIONS);
-    break_location_iterator.FindBreakLocationFromAddress(frame->pc());
+    // pc points to the instruction after the current one, possibly a break
+    // location as well. So the "- 1" to exclude it from the search.
+    break_location_iterator.FindBreakLocationFromAddress(frame->pc() - 1);
     if (break_location_iterator.IsExit()) {
       // We are within the return sequence. At the momemt it is not possible to
       // get a source position which is consistent with the current scope chain.
       // Thus all nested with, catch and block contexts are skipped and we only
       // provide the function scope.
       if (scope_info->HasContext()) {
         context_ = Handle<Context>(context_->declaration_context(), isolate_);
       } else {
         while (context_->closure() == *function_) {
           context_ = Handle<Context>(context_->previous(), isolate_);
@@ skipping 2388 matching lines @@
     // Handle last resort GC and make sure to allow future allocations
     // to grow the heap without causing GCs (if possible).
     isolate->counters()->gc_last_resort_from_js()->Increment();
     isolate->heap()->CollectAllGarbage(Heap::kNoGCFlags,
                                        "Runtime::PerformGC");
   }
 }
 
 
 } }  // namespace v8::internal