[bfcache] Always call CanStoreDocument for the main frame

Ensure that we always pass the main document to CanStoreDocument as
CanStoreDocument always returns false for non-main documents, which
then will lead to eviction even when we still can store the document
in the cache.

R=arthursonzogni@chromium.org,hajimehoshi@chromium.org

Change-Id: I021ef8fa0505c9d8eef0d423cde319439f4c612e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1905688
Commit-Queue: Alexander Timin <altimin@chromium.org>
Reviewed-by: Arthur Sonzogni <arthursonzogni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#717500}

content/browser/back_forward_cache_browsertest.cc

@@ -3921,4 +3921,39 @@ IN_PROC_BROWSER_TEST_F(SensorBackForwardCacheBrowserTest,
       FROM_HERE);
 }
 
+IN_PROC_BROWSER_TEST_F(BackForwardCacheBrowserTest,
+                       AllowedFeaturesForSubframesDoNotEvict) {
+  // The main purpose of this test is to check that when a state of a subframe
+  // is updated, CanStoreDocument is still called for the main frame - otherwise
+  // we would always evict the document, even when the feature is allowed as
+  // CanStoreDocument always returns false for non-main frames.
+
+  ASSERT_TRUE(embedded_test_server()->Start());
+  GURL url_a(embedded_test_server()->GetURL(
+      "a.com", "/cross_site_iframe_factory.html?a(b)"));
+  GURL url_c(embedded_test_server()->GetURL("c.com", "/title1.html"));
+
+  // 1) Navigate to A.
+  ASSERT_TRUE(NavigateToURL(shell(), url_a));
+  RenderFrameHostImpl* rfh_a = current_frame_host();
+  RenderFrameHostImpl* rfh_b = rfh_a->child_at(0)->current_frame_host();
+  RenderFrameDeletedObserver delete_observer_rfh_b(rfh_b);
+
+  // 2) Navigate to C.
+  ASSERT_TRUE(NavigateToURL(shell(), url_c));
+
+  // 3) No-op feature update on a subframe while in cache, should be no-op.
+  ASSERT_FALSE(delete_observer_rfh_b.deleted());
+  static_cast<blink::mojom::LocalFrameHost*>(rfh_b)
+      ->DidChangeActiveSchedulerTrackedFeatures(0);
+
+  // 4) Go back.
+  web_contents()->GetController().GoBack();
+  EXPECT_TRUE(WaitForLoadStop(shell()->web_contents()));
+  EXPECT_EQ(current_frame_host(), rfh_a);
+
+  ExpectOutcome(BackForwardCacheMetrics::HistoryNavigationOutcome::kRestored,
+                FROM_HERE);
+}
+
 }  // namespace content

content/browser/frame_host/render_frame_host_impl.cc

@@ -7821,9 +7821,14 @@ void RenderFrameHostImpl::MaybeEvictFromBackForwardCache() {
   if (!is_in_back_forward_cache_)
     return;
 
+  RenderFrameHostImpl* top_document = this;
+  while (RenderFrameHostImpl* parent = top_document->GetParent())
+    top_document = parent;
+
   NavigationControllerImpl* controller = static_cast<NavigationControllerImpl*>(
       frame_tree_node_->navigator()->GetController());
-  auto can_store = controller->GetBackForwardCache().CanStoreDocument(this);
+  auto can_store =
+      controller->GetBackForwardCache().CanStoreDocument(top_document);
   TRACE_EVENT1("navigation",
                "RenderFrameHostImpl::MaybeEvictFromBackForwardCache",
                "can_store", can_store.ToString());