Make sure to check if we have a hint in the cache before racing navigation

I left the SRP check there since that contains more hosts and doing the
HasHint check for every host is probably not worth it.

Bug: 1022624
Change-Id: I1b4c782df2c9fb76e08e09d3674178420a5a3728
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1904822Reviewed-by: Michael Crouse <mcrouse@chromium.org>
Reviewed-by: Tarun Bansal <tbansal@chromium.org>
Commit-Queue: Sophie Chang <sophiechang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#713714}

chrome/browser/optimization_guide/optimization_guide_hints_manager.cc

@@ -935,7 +935,8 @@ void OptimizationGuideHintsManager::OnNavigationStartOrRedirect(
     return;
   }
 
-  if (IsAllowedToFetchNavigationHints(navigation_handle->GetURL())) {
+  if (IsAllowedToFetchNavigationHints(navigation_handle->GetURL()) &&
+      !hint_cache_->HasHint(navigation_handle->GetURL().host())) {
     std::vector<std::string> hosts{navigation_handle->GetURL().host()};
     navigation_hosts_last_fetched_real_time_.clear();
     navigation_hosts_last_fetched_real_time_.push_back(

chrome/browser/optimization_guide/optimization_guide_hints_manager_unittest.cc

@@ -1941,6 +1941,30 @@ TEST_F(OptimizationGuideHintsManagerTest,
       "OptimizationGuide.HintsFetcher.GetHintsRequest.HostCount", 1, 1);
 }
 
+TEST_F(OptimizationGuideHintsManagerTest,
+       HintsFetchedAtNavigationTime_HasComponentHintButNotFetched) {
+  hints_manager()->RegisterOptimizationTypes(
+      {optimization_guide::proto::DEFER_ALL_SCRIPT});
+  base::test::ScopedFeatureList scoped_list;
+  scoped_list.InitAndEnableFeature(
+      optimization_guide::features::kOptimizationHintsFetching);
+  InitializeWithDefaultConfig("1.0.0.0");
+
+  // Set ECT estimate so hint is activated.
+  hints_manager()->OnEffectiveConnectionTypeChanged(
+      net::EffectiveConnectionType::EFFECTIVE_CONNECTION_TYPE_SLOW_2G);
+  std::unique_ptr<content::MockNavigationHandle> navigation_handle =
+      CreateMockNavigationHandleWithOptimizationGuideWebContentsObserver(
+          url_with_hints());
+  base::RunLoop run_loop;
+  base::HistogramTester histogram_tester;
+  hints_manager()->OnNavigationStartOrRedirect(navigation_handle.get(),
+                                               run_loop.QuitClosure());
+  run_loop.Run();
+  histogram_tester.ExpectTotalCount(
+      "OptimizationGuide.HintsFetcher.GetHintsRequest.HostCount", 0);
+}
+
 TEST_F(OptimizationGuideHintsManagerTest,
        HintsNotFetchedAtNavigationTime_ECT_4G) {
   hints_manager()->RegisterOptimizationTypes(