If replacing a safebrowsing interstitial, don't call DontProceed on the old one.

chrome/browser/safe_browsing/safe_browsing_blocking_page.cc

Index: chrome/browser/safe_browsing/safe_browsing_blocking_page.cc
diff --git a/chrome/browser/safe_browsing/safe_browsing_blocking_page.cc b/chrome/browser/safe_browsing/safe_browsing_blocking_page.cc
index 02986de5c35d02cb9acd08d044eb4f1dd03c3b53..a7715ef3bdeca2a4d53d4c027a4ba0fa5e72c786 100644
--- a/chrome/browser/safe_browsing/safe_browsing_blocking_page.cc
+++ b/chrome/browser/safe_browsing/safe_browsing_blocking_page.cc
@@ -454,19 +454,11 @@ void SafeBrowsingBlockingPage::ShowBlockingPage(
   DVLOG(1) << __func__ << " " << unsafe_resource.url.spec();
   WebContents* web_contents = unsafe_resource.web_contents_getter.Run();
 
-  InterstitialPage* interstitial =
-      InterstitialPage::GetInterstitialPage(web_contents);
-  if (interstitial && !unsafe_resource.is_subresource) {
-    // There is already an interstitial showing and we are about to display a
-    // new one for the main frame. Just hide the current one, it is now
-    // irrelevent
-    interstitial->DontProceed();
-    interstitial = NULL;
-  }
-
-  if (!interstitial) {
-    // There are no interstitial currently showing in that tab, go ahead and
-    // show this interstitial.
+  if (!InterstitialPage::GetInterstitialPage(web_contents) ||
+      !unsafe_resource.is_subresource) {
+    // There is no interstitial currently showing in that tab, or we are about
+    // to display a new one for the main frame. If there is already an
+    // interstitial, showing the new one will automatically hide the old one.

[Nathan Parker, 2016/11/17 20:08:24]

What causes the old one to get hidden?  And do we want a new one to show at all?
 It seems weird to have one show, then have another replace it.

[mattm, 2016/11/17 21:22:09]

https://cs.chromium.org/chromium/src/content/browser/frame_host/interstitial_...
I guess for the reload case, but this is the same path that gets hit if you see
a warning, type a different url into the omnibox, and then get a warning for
that page. Seems easier to just always display the new one than to add extra
code to try to figure out if it's the same as the old one.

     content::NavigationEntry* entry =
         unsafe_resource.GetNavigationEntryForResource();
     SafeBrowsingBlockingPage* blocking_page =