tools: Local tests for the speculative prefetch predictor.

chrome/browser/predictors/resource_prefetch_predictor.cc

 // Copyright 2014 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/predictors/resource_prefetch_predictor.h"
 
 #include <map>
 #include <set>
 #include <utility>
 
@@ skipping 504 matching lines @@
   }
   history_service_observer_.RemoveAll();
 }
 
 void ResourcePrefetchPredictor::OnMainFrameRequest(
     const URLRequestSummary& request) {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
   DCHECK_EQ(INITIALIZED, initialization_state_);
 
   const GURL& main_frame_url = request.navigation_id.main_frame_url;
-  StartPrefetching(main_frame_url);
+  if (!config_.ExternalPrefetchingOnly())

[pasko, 2016/11/17 15:59:04]

so 'external prefetch only' disables all prefetching or am I missing something?

[Benoit L, 2016/11/21 13:40:32]

It disables prefetches triggered by observing a navigation, but not ones from
directly calling ResourcePrefetchPredictor::StartPrefetching.

Added a comment in the place where this flag is defined.

+    StartPrefetching(main_frame_url);
 
   // Cleanup older navigations.
   CleanupAbandonedNavigations(request.navigation_id);
 
   // New empty navigation entry.
   inflight_navigations_.insert(
       std::make_pair(request.navigation_id,
                      base::MakeUnique<PageRequestSummary>(main_frame_url)));
 }
 
@@ skipping 633 matching lines @@
 TestObserver::~TestObserver() {
   predictor_->SetObserverForTesting(nullptr);
 }
 
 TestObserver::TestObserver(ResourcePrefetchPredictor* predictor)
     : predictor_(predictor) {
   predictor_->SetObserverForTesting(this);
 }
 
 }  // namespace predictors