Revert of OOPIF: Fix subframe back/forward after recreating FTNs.

content/browser/frame_host/navigation_entry_impl.h

Index: content/browser/frame_host/navigation_entry_impl.h
diff --git a/content/browser/frame_host/navigation_entry_impl.h b/content/browser/frame_host/navigation_entry_impl.h
index 801a72bc23a43df71cec742ad30926f3fb7e5c40..5907b6c2bd5992a25d6671a20c1c8ad3582da799 100644
--- a/content/browser/frame_host/navigation_entry_impl.h
+++ b/content/browser/frame_host/navigation_entry_impl.h
@@ -37,11 +37,8 @@
     TreeNode(FrameNavigationEntry* frame_entry);
     ~TreeNode();
 
-    // Returns whether this TreeNode corresponds to |frame_tree_node|, based on
-    // the FrameTreeNode ID or unique name.  If the unique name matches and
-    // FrameTreeNode ID does not, then this will update the entry's
-    // FrameTreeNode ID (which may be stale if the node was recreated).
-    bool MatchesFrame(FrameTreeNode* frame_tree_node);
+    // Returns whether this TreeNode corresponds to |frame_tree_node|.
+    bool MatchesFrame(FrameTreeNode* frame_tree_node) const;
 
     // Recursively makes a deep copy of TreeNode with copies of each of the
     // FrameNavigationEntries in the subtree.  Replaces the TreeNode
@@ -52,7 +49,7 @@
     // NavigationEntries of the same tab.
     std::unique_ptr<TreeNode> CloneAndReplace(
         FrameTreeNode* frame_tree_node,
-        FrameNavigationEntry* frame_navigation_entry);
+        FrameNavigationEntry* frame_navigation_entry) const;
 
     // Ref counted pointer that keeps the FrameNavigationEntry alive as long as
     // it is needed by this node's NavigationEntry.
@@ -191,6 +188,7 @@
   // Does nothing if there is no entry already and |url| is about:blank, since
   // that does not count as a real commit.
   void AddOrUpdateFrameEntry(FrameTreeNode* frame_tree_node,
+                             const std::string& frame_unique_name,
                              int64_t item_sequence_number,
                              int64_t document_sequence_number,
                              SiteInstanceImpl* site_instance,
@@ -199,10 +197,17 @@
                              const PageState& page_state);
 
   // Returns the FrameNavigationEntry corresponding to |frame_tree_node|, if
-  // there is one in this NavigationEntry. This compares against the
-  // FrameTreeNode ID first, and if that doesn't match, then the unique_name.
-  // It will update the FrameNavigationEntry's FrameTreeNode ID if it is stale.
-  FrameNavigationEntry* GetFrameEntry(FrameTreeNode* frame_tree_node);
+  // there is one in this NavigationEntry.
+  FrameNavigationEntry* GetFrameEntry(FrameTreeNode* frame_tree_node) const;
+
+  // Returns the FrameNavigationEntry corresponding to the frame with the given
+  // |unique_name|, if any. This is useful when the FrameTreeNode cannot be used
+  // to find the entry, such as for a newly created subframe in a history
+  // navigation. Callers should update the FrameTreeNode ID of the entry so that
+  // it can be found with |GetFrameEntry| above.
+  // TODO(creis): Generate or verify the unique_name in the browser process.
+  FrameNavigationEntry* GetFrameEntryByUniqueName(
+      const std::string& unique_name) const;
 
   void set_unique_id(int unique_id) {
     unique_id_ = unique_id;
@@ -359,7 +364,8 @@
 
  private:
   // Finds the TreeNode associated with |frame_tree_node|, if any.
-  NavigationEntryImpl::TreeNode* FindFrameEntry(FrameTreeNode* frame_tree_node);
+  NavigationEntryImpl::TreeNode* FindFrameEntry(
+      FrameTreeNode* frame_tree_node) const;
 
   // WARNING WARNING WARNING WARNING WARNING WARNING WARNING WARNING WARNING
   // Session/Tab restore save portions of this class so that it can be recreated