Send a subtree of same-process PageStates for back/forward child frames.

content/common/navigation_params.h

Index: content/common/navigation_params.h
diff --git a/content/common/navigation_params.h b/content/common/navigation_params.h
index 0937e4202609deb9abcc219e0e62ffd7c4a8c2ff..45ca6eb377afc1a364e6695eaf6b3c05b81eaa8a 100644
--- a/content/common/navigation_params.h
+++ b/content/common/navigation_params.h
@@ -226,7 +226,7 @@ struct CONTENT_EXPORT RequestNavigationParams {
                           int nav_entry_id,
                           bool is_same_document_history_load,
                           bool is_history_navigation_in_new_child,
-                          std::map<std::string, bool> subframe_unique_names,
+                          std::map<std::string, PageState> subtree_page_states,
                           bool has_committed_real_load,
                           bool intended_as_new_entry,
                           int pending_history_list_offset,
@@ -270,13 +270,13 @@ struct CONTENT_EXPORT RequestNavigationParams {
   bool is_history_navigation_in_new_child;
 
   // If this is a history navigation, this contains a map of frame unique names
-  // to |is_about_blank| for immediate children of the frame being navigated for
-  // which there are history items.  The renderer process only needs to check
-  // with the browser process for newly created subframes that have these unique
-  // names (and only when not staying on about:blank).
-  // TODO(creis): Expand this to a data structure including corresponding
-  // same-process PageStates for the whole subtree in https://crbug.com/639842.
-  std::map<std::string, bool> subframe_unique_names;
+  // to PageStates for all descendants of the frame being navigated that have
+  // history items.  When creating a new subframe during a back/forward
+  // navigation, the renderer can use these PageStates for newly created
+  // subframes.  Note that if the PageState is empty, it corresponds to a
+  // history item that will be loaded in a different process, and thus the
+  // renderer process should ask the browser process to handle it instead.
+  std::map<std::string, PageState> subtree_page_states;
 
   // Whether the frame being navigated has already committed a real page, which
   // affects how new navigations are classified in the renderer process.