Allow experimental configuration of IsolatedPrerender max body size

Also adds a test for documenting what happens when the limit is
reached.

Bug: 1115736
Change-Id: Ie488adb6b874ae47503670514bd7456bef8bfd6f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2354536Reviewed-by: Ryan Sturm <ryansturm@chromium.org>
Commit-Queue: Robert Ogden <robertogden@chromium.org>
Cr-Commit-Position: refs/heads/master@{#797776}

chrome/browser/prerender/isolated/isolated_prerender_params.cc

@@ -65,6 +65,12 @@ IsolatedPrerenderMaximumNumberOfNoStatePrefetchAttempts() {
   return max;
 }
 
+size_t IsolatedPrerenderMainframeBodyLengthLimit() {
+  return 1024 * base::GetFieldTrialParamByFeatureAsInt(
+                    features::kIsolatePrerenders,
+                    "max_mainframe_body_length_kb", 5 * 1024);
+}
+
 size_t IsolatedPrerenderMaximumNumberOfConcurrentPrefetches() {
   return static_cast<size_t>(base::GetFieldTrialParamByFeatureAsInt(
       features::kIsolatePrerenders, "max_concurrent_prefetches", 1));

chrome/browser/prerender/isolated/isolated_prerender_params.h

@@ -34,6 +34,10 @@ size_t IsolatedPrerenderMaximumNumberOfConcurrentPrefetches();
 base::Optional<size_t>
 IsolatedPrerenderMaximumNumberOfNoStatePrefetchAttempts();
 
+// The maximum body length allowed to be prefetched for mainframe responses in
+// bytes.
+size_t IsolatedPrerenderMainframeBodyLengthLimit();
+
 // Whether idle sockets should be closed after every prefetch.
 bool IsolatedPrerenderCloseIdleSockets();
 

chrome/browser/prerender/isolated/isolated_prerender_tab_helper.cc

@@ -677,7 +677,7 @@ void IsolatedPrerenderTabHelper::StartSinglePrefetch() {
       GetURLLoaderFactory(),
       base::BindOnce(&IsolatedPrerenderTabHelper::OnPrefetchComplete,
                      base::Unretained(this), loader.get(), url, isolation_info),
-      1024 * 1024 * 5 /* 5MB */);
+      IsolatedPrerenderMainframeBodyLengthLimit());
 
   page_->url_loaders_.emplace(std::move(loader));
 }

chrome/browser/prerender/isolated/isolated_prerender_tab_helper_unittest.cc

@@ -811,6 +811,50 @@ TEST_F(IsolatedPrerenderTabHelperTest, NetErrorOKOnly) {
       "IsolatedPrerender.Prefetch.Mainframe.TotalRedirects", 0, 1);
 }
 
+TEST_F(IsolatedPrerenderTabHelperTest, ResponseBodyLimit) {
+  base::HistogramTester histogram_tester;
+  base::test::ScopedFeatureList scoped_feature_list;
+  scoped_feature_list.InitAndEnableFeatureWithParameters(
+      features::kIsolatePrerenders, {{"max_mainframe_body_length_kb", "0"}});
+
+  NavigateSomewhere();
+  GURL doc_url("https://www.google.com/search?q=cats");
+  GURL prediction_url("https://www.cat-food.com/");
+  MakeNavigationPrediction(web_contents(), doc_url, {prediction_url});
+
+  network::ResourceRequest request = VerifyCommonRequestState(prediction_url);
+  MakeResponseAndWait(net::HTTP_OK, net::OK, kHTMLMimeType, /*headers=*/{},
+                      kHTMLBody);
+
+  EXPECT_EQ(predicted_urls_count(), 1U);
+  EXPECT_EQ(prefetch_eligible_count(), 1U);
+  EXPECT_EQ(prefetch_attempted_count(), 1U);
+  EXPECT_EQ(prefetch_successful_count(), 0U);
+  EXPECT_EQ(prefetch_total_redirect_count(), 0U);
+  EXPECT_TRUE(navigation_to_prefetch_start().has_value());
+
+  histogram_tester.ExpectUniqueSample(
+      "IsolatedPrerender.Prefetch.Mainframe.NetError",
+      std::abs(net::ERR_INSUFFICIENT_RESOURCES), 1);
+  histogram_tester.ExpectTotalCount(
+      "IsolatedPrerender.Prefetch.Mainframe.RespCode", 0);
+  histogram_tester.ExpectTotalCount(
+      "IsolatedPrerender.Prefetch.Mainframe.BodyLength", 0);
+  histogram_tester.ExpectTotalCount(
+      "IsolatedPrerender.Prefetch.Mainframe.TotalTime", 0);
+  histogram_tester.ExpectTotalCount(
+      "IsolatedPrerender.Prefetch.Mainframe.ConnectTime", 0);
+
+  NavigateAndVerifyPrefetchStatus(
+      prediction_url,
+      IsolatedPrerenderTabHelper::PrefetchStatus::kPrefetchFailedNetError);
+  EXPECT_EQ(after_srp_prefetch_eligible_count(), 1U);
+  EXPECT_EQ(base::Optional<size_t>(0), after_srp_clicked_link_srp_position());
+
+  histogram_tester.ExpectUniqueSample(
+      "IsolatedPrerender.Prefetch.Mainframe.TotalRedirects", 0, 1);
+}
+
 TEST_F(IsolatedPrerenderTabHelperTest, NonHTML) {
   base::HistogramTester histogram_tester;
   base::test::ScopedFeatureList scoped_feature_list;