[bfcache] Properly evict pages when cache is too large.

Calling EvictFromBackForwardCache() is better than directly deleting the
RenderFrameHostImpl, because it matches the behavior when the document
is evicted for other reasons (e.g. cache expiration, use of unsupported
features).

Change-Id: If76feb222b2496fb2431dd20892fd46a1f734bd4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1809163Reviewed-by: Alexander Timin <altimin@chromium.org>
Reviewed-by: Arthur Sonzogni <arthursonzogni@chromium.org>
Commit-Queue: Lowell Manners <lowell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#697269}

content/browser/frame_host/back_forward_cache.cc

@@ -177,12 +177,14 @@ void BackForwardCache::StoreDocument(std::unique_ptr<RenderFrameHostImpl> rfh) {
   size_t size_limit = cache_size_limit_for_testing_
                           ? cache_size_limit_for_testing_
                           : kBackForwardCacheLimit;
-
-  // Remove the last recently used document if the BackForwardCache list is
+  // Evict the least recently used documents if the BackForwardCache list is
   // full.
-  if (render_frame_hosts_.size() > size_limit) {
-    // TODO(arthursonzogni): Handle RenderFrame deletion appropriately.
-    render_frame_hosts_.pop_back();
+  size_t available_count = 0;
+  for (auto& frame_host : render_frame_hosts_) {
+    if (frame_host->is_evicted_from_back_forward_cache())
+      continue;
+    if (++available_count > size_limit)
+      frame_host->EvictFromBackForwardCache();
   }
 }