Enable download page action for error page

components/error_page/renderer/net_error_helper_core.cc

Index: components/error_page/renderer/net_error_helper_core.cc
diff --git a/components/error_page/renderer/net_error_helper_core.cc b/components/error_page/renderer/net_error_helper_core.cc
index 13cb441b68719209c6fa29d25ae5aa99e3aadcd4..041b0ed3d56db871b939727486264650e07ec717 100644
--- a/components/error_page/renderer/net_error_helper_core.cc
+++ b/components/error_page/renderer/net_error_helper_core.cc
@@ -583,6 +583,8 @@ void NetErrorHelperCore::OnStartLoad(FrameType frame_type, PageType page_type) {
   // or the new page is not an error page, then reset pending error page state.
   if (!pending_error_page_info_ || page_type != ERROR_PAGE)
     CancelPendingFetches();
+
+  delegate_->SetIsShowingDownloadButton(false);

[mmenke, 2017/01/03 16:20:10]

Bug:  What we're showing only changes on commit, not when a load starts.  Loads
may be aborted.

Due to the complexities of the state machine, I'd rather not add additional
top-level variables related to state of the currently displayed error page.  Any
additional state should be added to ErrorPageInfo.

[jianli, 2017/01/06 23:46:37]

Since we already have one in ErrorPageInfo, download_button_in_page, I think we
can remove this one.

 }
 
 void NetErrorHelperCore::OnCommitLoad(FrameType frame_type, const GURL& url) {
@@ -658,6 +660,9 @@ void NetErrorHelperCore::OnFinishLoad(FrameType frame_type) {
     RecordEvent(NETWORK_ERROR_PAGE_CACHED_COPY_BUTTON_SHOWN);
   }
 
+  delegate_->SetIsShowingDownloadButton(
+      committed_error_page_info_->download_button_in_page);
+
   delegate_->EnablePageHelperFunctions();
 
   if (committed_error_page_info_->needs_load_navigation_corrections) {