OOPIF: Support session restore by combining/splitting frame states.

content/browser/frame_host/navigation_controller_impl.cc

Index: content/browser/frame_host/navigation_controller_impl.cc
diff --git a/content/browser/frame_host/navigation_controller_impl.cc b/content/browser/frame_host/navigation_controller_impl.cc
index 194a0e87499083a111e4e0f7db41cbe078dba168..c2b1bdd9eefd39230ea9e4cd05f0f142df97f6a1 100644
--- a/content/browser/frame_host/navigation_controller_impl.cc
+++ b/content/browser/frame_host/navigation_controller_impl.cc
@@ -750,7 +750,7 @@ void NavigationControllerImpl::LoadURLWithParams(const LoadURLParams& params) {
         entry = GetLastCommittedEntry()->Clone();
         entry->SetPageID(-1);
         entry->AddOrUpdateFrameEntry(node, "", -1, -1, nullptr, params.url,
-                                     params.referrer, PageState());
+                                     params.referrer, ExplodedFrameState());
       }
     }
   }
@@ -900,7 +900,10 @@ bool NavigationControllerImpl::RendererDidNavigate(
 
   // All committed entries should have nonempty content state so WebKit doesn't
   // get confused when we go back to them (see the function for details).
-  DCHECK(params.page_state.IsValid());
+  if (SiteIsolationPolicy::UseSubframeNavigationEntries())
+    DCHECK(params.frame_state.item_sequence_number);
+  else
+    DCHECK(params.page_state.IsValid());
   NavigationEntryImpl* active_entry = GetLastCommittedEntry();
   active_entry->SetTimestamp(timestamp);
   active_entry->SetHttpStatusCode(params.http_status_code);
@@ -910,8 +913,10 @@ bool NavigationControllerImpl::RendererDidNavigate(
         active_entry->GetFrameEntry(rfh->frame_tree_node());
     // We may not find a frame_entry in some cases; ignore the PageState if so.
     // TODO(creis): Remove the "if" once https://crbug.com/522193 is fixed.
-    if (frame_entry)
-      frame_entry->set_page_state(params.page_state);
+    if (frame_entry) {
+      frame_entry->set_frame_state(params.frame_state);
+      active_entry->UpdatePageState();
+    }
   } else {
     active_entry->SetPageState(params.page_state);
   }
@@ -1324,7 +1329,8 @@ bool NavigationControllerImpl::RendererDidNavigateAutoSubframe(
     last_committed->AddOrUpdateFrameEntry(
         rfh->frame_tree_node(), params.frame_unique_name,
         params.item_sequence_number, params.document_sequence_number,
-        rfh->GetSiteInstance(), params.url, params.referrer, params.page_state);
+        rfh->GetSiteInstance(), params.url, params.referrer,
+        params.frame_state);
 
     // Cross-process subframe navigations may leave a pending entry around.
     // Clear it if it's actually for the subframe.
@@ -1847,11 +1853,12 @@ void NavigationControllerImpl::FindFramesToNavigate(
     return;
 
   // Schedule a load in this frame if the new item isn't for the same item
-  // sequence number in the same SiteInstance.
-  // TODO(creis): Handle null SiteInstances during session restore.
+  // sequence number in the same SiteInstance. Newly restored items may not have
+  // SiteInstances yet, in which case it will be assigned on first commit.
   if (!old_item ||
       new_item->item_sequence_number() != old_item->item_sequence_number() ||
-      new_item->site_instance() != old_item->site_instance()) {
+      (new_item->site_instance() != nullptr &&
+       new_item->site_instance() != old_item->site_instance())) {
     if (old_item &&
         new_item->document_sequence_number() ==
             old_item->document_sequence_number()) {