Add a target_frame_id to the history serialization format.

content/public/renderer/history_item_serialization.cc

Index: content/public/renderer/history_item_serialization.cc
diff --git a/content/public/renderer/history_item_serialization.cc b/content/public/renderer/history_item_serialization.cc
index 6bef7de3f3c392fa8bb50f6ab5791e21e253e6fb..9bf7e41af635071c93f3852947b862ab0510198a 100644
--- a/content/public/renderer/history_item_serialization.cc
+++ b/content/public/renderer/history_item_serialization.cc
@@ -91,6 +91,7 @@ bool RecursivelyGenerateFrameState(const WebHistoryItem& item,
   state->item_sequence_number = item.itemSequenceNumber();
   state->document_sequence_number =
       item.documentSequenceNumber();
+  state->target_frame_id = item.targetFrameID();
   state->page_scale_factor = item.pageScaleFactor();
   ToNullableString16Vector(item.documentState(), &state->document_state);
 
@@ -138,6 +139,8 @@ bool RecursivelyGenerateHistoryItem(const ExplodedFrameState& state,
     item->setItemSequenceNumber(state.item_sequence_number);
   if (state.document_sequence_number)
     item->setDocumentSequenceNumber(state.document_sequence_number);
+  if (state.target_frame_id)

[darin (slow to review), 2013/10/29 23:05:50]

The above comment does not apply to target frame ID. Setting a value of 0 seems
OK for frame ID. We should probably treat this property more like
setPageScaleFactor, right?

[Nate Chapin, 2013/10/29 23:16:26]

That's probably true. Will fix.

+    item->setTargetFrameID(state.target_frame_id);
 
   item->setHTTPContentType(state.http_body.http_content_type);
   if (!state.http_body.is_null) {