Transform redirect chains for the Safe Browsing subresource filter.

chrome/browser/renderer_host/safe_browsing_resource_throttle.cc

Index: chrome/browser/renderer_host/safe_browsing_resource_throttle.cc
diff --git a/chrome/browser/renderer_host/safe_browsing_resource_throttle.cc b/chrome/browser/renderer_host/safe_browsing_resource_throttle.cc
index a917f501a18c2fdcd31cfcfbec68f092e377a83e..39050e89cb43610df3f59c73711b654340476ba5 100644
--- a/chrome/browser/renderer_host/safe_browsing_resource_throttle.cc
+++ b/chrome/browser/renderer_host/safe_browsing_resource_throttle.cc
@@ -300,13 +300,28 @@ void SafeBrowsingResourceThrottle::StartDisplayingBlockingPage(
     prerender::PrerenderContents* prerender_contents =
         prerender::PrerenderContents::FromWebContents(web_contents);
 
-    subresource_filter::ContentSubresourceFilterDriverFactory* driver_factory =
-        subresource_filter::ContentSubresourceFilterDriverFactory::
-            FromWebContents(web_contents);
-    DCHECK(driver_factory);
-    driver_factory->OnMainResourceMatchedSafeBrowsingBlacklist(
-        resource.url, resource.redirect_urls, resource.threat_type,
-        resource.threat_metadata.threat_pattern_type);
+    // Once activated, the subresource filter will filters subresources, but is
+    // triggered when the main frame document matches Safe Browsing blacklists.
+    if (!resource.is_subresource) {
+      using subresource_filter::ContentSubresourceFilterDriverFactory;
+      ContentSubresourceFilterDriverFactory* driver_factory =
+          ContentSubresourceFilterDriverFactory::FromWebContents(web_contents);
+      DCHECK(driver_factory);
+
+      // For a redirect chain of A -> B -> C, the subresource filter expects C
+      // as the resource URL and [A, B] as redirect URLs.
+      std::vector<GURL> redirect_parent_urls;
+      if (!resource.redirect_urls.empty()) {
+        redirect_parent_urls.push_back(resource.original_url);
+        redirect_parent_urls.insert(redirect_parent_urls.end(),
+                                    resource.redirect_urls.begin(),
+                                    --resource.redirect_urls.end());

[Nathan Parker, 2016/09/15 21:19:45]

How does decrement work on a const iterator? Is that shortening
resource.reidrect_urls?  Maybe you want .end() - 1. 

Might be good to have a unit test for this.

[engedy, 2016/09/16 09:04:43]

It works as you'd expect it to, i.e. the temporary const_iterator instance that
is created by end() is advanced backwards by one. Nevertheless, I have changed
it to std::prev(...) for better readability.
 
Tests on the way!

+      }
+
+      driver_factory->OnMainResourceMatchedSafeBrowsingBlacklist(
+          resource.url, redirect_parent_urls, resource.threat_type,
+          resource.threat_metadata.threat_pattern_type);
+    }
 
     if (prerender_contents) {
       prerender_contents->Destroy(prerender::FINAL_STATUS_SAFE_BROWSING);