Speculative resource prefetching - fixing missing navigations due to server side redirects.

chrome/browser/net/resource_prefetch_predictor_observer.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/net/resource_prefetch_predictor_observer.h"
 
 #include <string>
 
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/resource_request_info.h"
+#include "net/http/http_response_headers.h"
 #include "net/url_request/url_request.h"
 
 using content::BrowserThread;
 using predictors::ResourcePrefetchPredictor;
 
 namespace {
 
 bool SummarizeResponse(net::URLRequest* request,
                        ResourcePrefetchPredictor::URLRequestSummary* summary) {
   const content::ResourceRequestInfo* info =
@@ skipping 11 matching lines @@
 
   summary->navigation_id.render_process_id = render_process_id;
   summary->navigation_id.render_view_id = render_view_id;
   summary->navigation_id.main_frame_url = request->first_party_for_cookies();
   summary->navigation_id.creation_time = request->creation_time();
   summary->resource_url = request->original_url();
   summary->resource_type = info->GetResourceType();
   request->GetMimeType(&summary->mime_type);
   summary->was_cached = request->was_cached();
 
+  // Try to determine if this is a redirect response.
+  net::HttpResponseHeaders* headers = request->response_headers();
+  if (headers) {

[mmenke, 2012/08/01 15:39:53]

Rather than muck with the full set of headers, can't we just have
ChromeResourceDispatcherHostDelegate::OnRequestRedirected pass along
response->head.final_url?  Not sure if we care about HSTS, but I'm not sure if
net::URLRequestRedirectJob generates any fake response headers.

[mmenke, 2012/08/01 15:59:00]

Err...  That's not quite right.  I'd suggest modifying the delegate's
OnDidLoadResourceFromMemoryCache to take in new_url as an argument, and just
pass that along.  Seems weird to get it from the headers again, when our caller,
a function of the same name, already takes it as an argument.

[Shishir, 2012/08/01 18:07:49]

Done.

[Shishir, 2012/08/01 18:07:49]

Passing on the redirect url.

+    std::string value;
+    if (headers->IsRedirect(&value)) {
+      summary->redirect_url = request->url().Resolve(value);
+      if (!summary->redirect_url.is_valid())
+        summary->redirect_url = GURL();
+    }
+  }
+
   // We want to rely on the mime_type to determine the resource type since we
   // dont want types such as PREFETCH, SUB_RESOURCE, etc.
   summary->resource_type =
       ResourcePrefetchPredictor::GetResourceTypeFromMimeType(
           summary->mime_type,
           summary->resource_type);
   return true;
 }
 
 }  // namespace
@@ skipping 66 matching lines @@
 
   BrowserThread::PostTask(
       BrowserThread::UI,
       FROM_HERE,
       base::Bind(&ResourcePrefetchPredictor::RecordUrlResponse,
                  predictor_,
                  summary));
 }
 
 }  // namespace chrome_browser_net