[Prerender] Restore request priorities when swapped in

chrome/browser/prerender/prerender_browsertest.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 <stddef.h>
 #include <deque>
 #include <set>
 #include <string>
 #include <unordered_map>
 #include <utility>
@@ skipping 125 matching lines @@
 using content::Referrer;
 using content::RenderFrameHost;
 using content::RenderViewHost;
 using content::RenderWidgetHost;
 using content::TestNavigationObserver;
 using content::WebContents;
 using content::WebContentsObserver;
 using net::NetworkChangeNotifier;
 using prerender::test_utils::RequestCounter;
 using prerender::test_utils::CreateCountingInterceptorOnIO;
-using prerender::test_utils::CreateHangingFirstRequestInterceptorOnIO;
+using prerender::test_utils::CreateHangingFirstRequestInterceptor;
 using prerender::test_utils::CreateMockInterceptorOnIO;
 using prerender::test_utils::TestPrerender;
 using prerender::test_utils::TestPrerenderContents;
 using task_manager::browsertest_util::WaitForTaskManagerRows;
 
 // crbug.com/708158
 #if !defined(OS_MACOSX) || !defined(ADDRESS_SANITIZER)
 
 // Prerender tests work as follows:
 //
@@ skipping 375 matching lines @@
       base::FilePath(FILE_PATH_LITERAL("prerender")),
       base::FilePath().AppendASCII(file_name));
 }
 
 page_load_metrics::PageLoadExtraInfo GenericPageLoadExtraInfo(
     const GURL& dest_url) {
   return page_load_metrics::PageLoadExtraInfo::CreateForTesting(
       dest_url, false /* started_in_foreground */);
 }
 
+// Helper function, to allow passing a UI closure to
+// CreateHangingFirstRequestInterceptor() instead of a IO callback.
+base::Callback<void(net::URLRequest*)> GetIOCallbackFromUIClosure(
+    base::Closure ui_closure) {
+  auto lambda = [](base::Closure closure, net::URLRequest*) {
+    content::BrowserThread::PostTask(content::BrowserThread::UI, FROM_HERE,
+                                     closure);
+  };
+  return base::Bind(lambda, ui_closure);
+}
+
 }  // namespace
 
 class PrerenderBrowserTest : public test_utils::PrerenderInProcessBrowserTest {
  public:
   PrerenderBrowserTest()
       : call_javascript_(true),
         check_load_events_(true),
         loader_path_("/prerender/prerender_loader.html") {}
 
   ~PrerenderBrowserTest() override {}
@@ skipping 743 matching lines @@
 #define MAYBE_PrerenderNoCommitNoSwap PrerenderNoCommitNoSwap
 #endif
 // Checks that the prerendering of a page is canceled correctly if we try to
 // swap it in before it commits.
 IN_PROC_BROWSER_TEST_F(PrerenderBrowserTest, MAYBE_PrerenderNoCommitNoSwap) {
   // Navigate to a page that triggers a prerender for a URL that never commits.
   const GURL kNoCommitUrl("http://never-respond.example.com");
   base::FilePath file(GetTestPath("prerender_page.html"));
 
   base::RunLoop prerender_start_loop;
-  BrowserThread::PostTask(
-      BrowserThread::IO, FROM_HERE,
-      base::Bind(&CreateHangingFirstRequestInterceptorOnIO, kNoCommitUrl, file,
-                 prerender_start_loop.QuitClosure()));
+  CreateHangingFirstRequestInterceptor(
+      kNoCommitUrl, file,
+      GetIOCallbackFromUIClosure(prerender_start_loop.QuitClosure()));
   DisableJavascriptCalls();
   PrerenderTestURL(kNoCommitUrl,
                    FINAL_STATUS_NAVIGATION_UNCOMMITTED,
                    0);
   // Wait for the hanging request to be scheduled.
   prerender_start_loop.Run();
 
   // Navigate to the URL, but assume the contents won't be swapped in.
   NavigateToDestURLWithDisposition(WindowOpenDisposition::CURRENT_TAB, false);
 }
 
 // crbug.com/708158
 #if defined(OS_MACOSX) && defined(ADDRESS_SANITIZER)
 #define MAYBE_PrerenderNoCommitNoSwap2 DISABLED_PrerenderNoCommitNoSwap2
 #else
 #define MAYBE_PrerenderNoCommitNoSwap2 PrerenderNoCommitNoSwap2
 #endif
 // Checks that client redirects don't add alias URLs until after they commit.
 IN_PROC_BROWSER_TEST_F(PrerenderBrowserTest, MAYBE_PrerenderNoCommitNoSwap2) {
   // Navigate to a page that then navigates to a URL that never commits.
   const GURL kNoCommitUrl("http://never-respond.example.com");
   base::FilePath file(GetTestPath("prerender_page.html"));
 
   base::RunLoop prerender_start_loop;
-  BrowserThread::PostTask(
-      BrowserThread::IO, FROM_HERE,
-      base::Bind(&CreateHangingFirstRequestInterceptorOnIO, kNoCommitUrl, file,
-                 prerender_start_loop.QuitClosure()));
+  CreateHangingFirstRequestInterceptor(
+      kNoCommitUrl, file,
+      GetIOCallbackFromUIClosure(prerender_start_loop.QuitClosure()));
   DisableJavascriptCalls();
   PrerenderTestURL(CreateClientRedirect(kNoCommitUrl.spec()),
                    FINAL_STATUS_APP_TERMINATING, 1);
   // Wait for the hanging request to be scheduled.
   prerender_start_loop.Run();
 
   // Navigating to the second URL should not swap.
   NavigateToURLWithDisposition(kNoCommitUrl, WindowOpenDisposition::CURRENT_TAB,
                                false);
 }
@@ skipping 1137 matching lines @@
   destruction_observer.Wait();
 }
 
 // Checks that a hanging unload on the referring page of a prerender swap does
 // not crash the browser on exit.
 IN_PROC_BROWSER_TEST_F(PrerenderBrowserTest, PrerenderHangingUnload) {
   // Matches URL in prerender_loader_with_unload.html.
   const GURL hang_url("http://unload-url.test");
   base::FilePath empty_file = ui_test_utils::GetTestFilePath(
       base::FilePath(), base::FilePath(FILE_PATH_LITERAL("empty.html")));
-  BrowserThread::PostTask(
-      BrowserThread::IO, FROM_HERE,
-      base::Bind(&CreateHangingFirstRequestInterceptorOnIO,
-                 hang_url, empty_file,
-                 base::Closure()));
+  CreateHangingFirstRequestInterceptor(
+      hang_url, empty_file, base::Callback<void(net::URLRequest*)>());
 
   set_loader_path("/prerender/prerender_loader_with_unload.html");
   PrerenderTestURL("/prerender/prerender_page.html", FINAL_STATUS_USED, 1);
   NavigateToDestURL();
 }
 
 
 // Checks that when the history is cleared, prerendering is cancelled and
 // prerendering history is cleared.
 IN_PROC_BROWSER_TEST_F(PrerenderBrowserTest, PrerenderClearHistory) {
@@ skipping 775 matching lines @@
                  done_url, empty_file, done_counter.AsWeakPtr()));
   // Loading may finish or be interrupted. The final result is important only.
   DisableLoadEventCheck();
   // TestPrenderContents is always created before the Autosignin JS can run, so
   // waiting for PrerenderContents to stop should be reliable.
   PrerenderTestURL("/password/autosignin.html",
                    FINAL_STATUS_CREDENTIAL_MANAGER_API, 0);
   EXPECT_EQ(0, done_counter.count());
 }
 
+// Checks that the requests from a prerender are IDLE priority before the swap
+// (except on Android), but normal priority after the swap.
+IN_PROC_BROWSER_TEST_F(PrerenderBrowserTest, ResourcePriority) {
+  GURL before_swap_url =
+      embedded_test_server()->GetURL("/prerender/image.jpeg");
+  GURL after_swap_url = embedded_test_server()->GetURL("/prerender/image.png");

[mattcary, 2017/04/14 09:28:46]

nit: if this gets in after cl/2819523002 (which is likely as it's being
submitted now) then there is a new GetURLWithReplacement utility function to use
instead of doing all the replacement text stuff yourself.

[droger, 2017/04/14 11:38:36]

Done.

+  base::StringPairs replacement_text;
+  replacement_text.push_back(
+      std::make_pair("REPLACE_WITH_IMAGE_URL", before_swap_url.spec()));
+  std::string replacement_path;
+  net::test_server::GetFilePathWithReplacements(
+      "/prerender/prerender_with_image.html", replacement_text,
+      &replacement_path);
+
+  // Setup request interceptors for subresources.
+  auto get_priority_lambda = [](net::RequestPriority* out_priority,
+                                net::URLRequest* request) {
+    *out_priority = request->priority();
+  };
+  RequestCounter before_swap_counter;
+  net::RequestPriority before_swap_priority = net::THROTTLED;
+  InterceptRequestAndCount(
+      before_swap_url, &before_swap_counter,
+      base::Bind(get_priority_lambda, &before_swap_priority));

[mattcary, 2017/04/14 09:28:46]

So before_swap_priority doesn't need to be base::Unretained because it's a basic
type and not a class? The documentation doesn't seem to be clear; I would have
thought that it would need to be unretained regardless.

[droger, 2017/04/14 11:38:36]

Done.

Unretained is often not used in these cases, but probably mostly because:

- Unretained actally does nothing, as opposed to other helpers such as Owned().

- the compiler will only enforce it for classes (and only for the callee object,
it will not even complain for the function parameters).

If you do:
Bind(&MyClass::MyFunction, my_instance, my_param), compilation will fail if you
omit the Unretained(my_instance). It does not check my_param though, and you can
get away without the Unretained there.


I'm not completely sure what is the best though. I made the change because I
could find a couple examples in the codebase, so it's probably a valid thing.

+  RequestCounter after_swap_counter;
+  net::RequestPriority after_swap_priority = net::THROTTLED;
+  InterceptRequestAndCount(
+      after_swap_url, &after_swap_counter,
+      base::Bind(get_priority_lambda, &after_swap_priority));
+
+  // Start the prerender.
+  PrerenderTestURL(replacement_path, FINAL_STATUS_USED, 1);
+
+  // Check priority before swap.
+  before_swap_counter.WaitForCount(1);
+#if defined(OS_ANDROID)
+  EXPECT_NE(net::IDLE, before_swap_priority);

[mattcary, 2017/04/14 09:28:46]

why not kDefaultImagePriority, as below?

[droger, 2017/04/14 11:38:36]

Done.

+#else
+  EXPECT_EQ(net::IDLE, before_swap_priority);
+#endif
+
+  // Swap.
+  NavigateToDestURL();
+
+  // Check priority after swap.
+  GetActiveWebContents()->GetMainFrame()->ExecuteJavaScriptForTests(
+      base::ASCIIToUTF16(
+          "var img=new Image(); img.src='/prerender/image.png'"));
+  after_swap_counter.WaitForCount(1);
+  EXPECT_NE(net::IDLE, after_swap_priority);
+}
+
+// Checks that a request started before the swap gets its original priority back
+// after the swap.
+IN_PROC_BROWSER_TEST_F(PrerenderBrowserTest, ResourcePriorityOverlappingSwap) {
+  GURL image_url = embedded_test_server()->GetURL("/prerender/image.jpeg");
+  base::StringPairs replacement_text;
+  replacement_text.push_back(
+      std::make_pair("REPLACE_WITH_IMAGE_URL", image_url.spec()));
+  std::string replacement_path;
+  net::test_server::GetFilePathWithReplacements(
+      "/prerender/prerender_with_image.html", replacement_text,
+      &replacement_path);
+
+  // Setup request interceptors for subresources.
+  net::URLRequest* url_request = nullptr;
+  net::RequestPriority priority = net::THROTTLED;
+  base::RunLoop wait_loop;
+  const net::RequestPriority kDefaultImagePriority = net::MEDIUM;
+  auto io_lambda = [](net::URLRequest** out_request,
+                      net::RequestPriority* out_priority, base::Closure closure,
+                      net::URLRequest* request) {
+    if (out_request)
+      *out_request = request;
+    content::BrowserThread::PostTask(
+        content::BrowserThread::UI, FROM_HERE,
+        base::Bind(
+            [](net::RequestPriority priority,
+               net::RequestPriority* out_priority, base::Closure closure) {
+              *out_priority = priority;
+              closure.Run();
+            },
+            request->priority(), out_priority, closure));
+  };
+
+  CreateHangingFirstRequestInterceptor(
+      image_url, base::FilePath(),
+      base::Bind(io_lambda, &url_request, &priority, wait_loop.QuitClosure()));
+
+  // The prerender will hang on the image resource, can't run the usual checks.
+  DisableLoadEventCheck();
+  DisableJavascriptCalls();
+  // Start the prerender.
+  PrerenderTestURL(replacement_path, FINAL_STATUS_USED, 0);
+
+  // Check priority before swap.
+  net::RequestPriority expected_priority =
+#if defined(OS_ANDROID)
+      kDefaultImagePriority;
+#else
+      net::IDLE;
+#endif
+  if (priority != expected_priority)
+    wait_loop.Run();
+  EXPECT_EQ(expected_priority, priority);
+
+  // Swap. Cannot use NavigateToDestURL, because it waits for the load to
+  // complete, but the resource is still hung.
+  current_browser()->OpenURL(content::OpenURLParams(
+      dest_url(), Referrer(), WindowOpenDisposition::CURRENT_TAB,
+      ui::PAGE_TRANSITION_TYPED, false));
+
+  // Check priority after swap.

[mattcary, 2017/04/14 09:28:46]

Clarify that the test will timeout if the priority isn't changed as expected.

[droger, 2017/04/14 11:38:36]

Done, and changed the test a bit so that it should be harder to timeout. It will
now timeout if the priority is never updated. No longer timeout if the priority
is updated to a wrong value.

+  priority = net::THROTTLED;
+  do {
+    base::RunLoop loop;
+    content::BrowserThread::PostTask(
+        content::BrowserThread::IO, FROM_HERE,
+        base::Bind(io_lambda, nullptr, &priority, loop.QuitClosure(),
+                   url_request));
+    loop.Run();
+  } while (priority != kDefaultImagePriority);
+}
+
 IN_PROC_BROWSER_TEST_F(PrerenderBrowserTest, FirstContentfulPaintTimingSimple) {
   GetPrerenderManager()->DisablePageLoadMetricsObserverForTesting();
   base::SimpleTestTickClock* clock = OverridePrerenderManagerTimeTicks();
   PrerenderTestURL("/prerender/prerender_page.html", FINAL_STATUS_USED, 1);
 
   base::TimeTicks load_start = clock->NowTicks();
   clock->Advance(base::TimeDelta::FromSeconds(1));
   NavigateToDestURL();
 
   PrerenderPageLoadMetricsObserver observer(GetPrerenderManager(),
@@ skipping 12 matching lines @@
   histogram_tester().ExpectUniqueSample(
       "Prerender.websame_PrefetchTTFCP.Warm.Cacheable.Visible", 1654, 1);
 }
 
 IN_PROC_BROWSER_TEST_F(PrerenderBrowserTest, FirstContentfulPaintTimingReuse) {
   GetPrerenderManager()->DisablePageLoadMetricsObserverForTesting();
   base::SimpleTestTickClock* clock = OverridePrerenderManagerTimeTicks();
 
   GURL url = embedded_test_server()->GetURL("/prerender/prerender_page.html");
   base::RunLoop hanging_request_waiter;
-  BrowserThread::PostTask(BrowserThread::IO, FROM_HERE,
-                          base::Bind(&CreateHangingFirstRequestInterceptorOnIO,
-                                     url, GetTestPath("prerender_page.html"),
-                                     hanging_request_waiter.QuitClosure()));
+  CreateHangingFirstRequestInterceptor(
+      url, GetTestPath("prerender_page.html"),
+      GetIOCallbackFromUIClosure(hanging_request_waiter.QuitClosure()));
   // As this load will be canceled, it is not waited for, and hence no
   // javascript is executed.
   DisableJavascriptCalls();
   PrerenderTestURL(url, FINAL_STATUS_CANCELLED, 0);
   hanging_request_waiter.Run();
 
   // This prerender cancels and reuses the first.
   clock->Advance(base::TimeDelta::FromSeconds(1));
   base::TimeTicks load_start = clock->NowTicks();
   EnableJavascriptCalls();
@@ skipping 64 matching lines @@
                        FirstContentfulPaintTimingNoCommit) {
   GetPrerenderManager()->DisablePageLoadMetricsObserverForTesting();
   base::SimpleTestTickClock* clock = OverridePrerenderManagerTimeTicks();
 
   GURL url = embedded_test_server()->GetURL("/prerender/prerender_page.html");
   base::FilePath url_file = ui_test_utils::GetTestFilePath(
       base::FilePath(),
       base::FilePath(FILE_PATH_LITERAL("prerender/prerender_page.html")));
 
   base::RunLoop prerender_start_loop;
-  BrowserThread::PostTask(
-      BrowserThread::IO, FROM_HERE,
-      base::Bind(&CreateHangingFirstRequestInterceptorOnIO, url, url_file,
-                 prerender_start_loop.QuitClosure()));
+  CreateHangingFirstRequestInterceptor(
+      url, url_file,
+      GetIOCallbackFromUIClosure(prerender_start_loop.QuitClosure()));
   // As this load is uncommitted, it is not waited for, and hence no
   // javascript is executed.
   DisableJavascriptCalls();
   PrerenderTestURL(url, FINAL_STATUS_NAVIGATION_UNCOMMITTED, 0);
   prerender_start_loop.Run();
 
   clock->Advance(base::TimeDelta::FromSeconds(1));
   NavigateToDestURLWithDisposition(WindowOpenDisposition::CURRENT_TAB, false);
 
   PrerenderPageLoadMetricsObserver observer(GetPrerenderManager(),
@@ skipping 96 matching lines @@
                        FirstContentfulPaintHiddenNoCommit) {
   GetPrerenderManager()->DisablePageLoadMetricsObserverForTesting();
   base::SimpleTestTickClock* clock = OverridePrerenderManagerTimeTicks();
 
   GURL url = embedded_test_server()->GetURL("/prerender/prerender_page.html");
   base::FilePath url_file = ui_test_utils::GetTestFilePath(
       base::FilePath(),
       base::FilePath(FILE_PATH_LITERAL("prerender/prerender_page.html")));
 
   base::RunLoop prerender_start_loop;
-  BrowserThread::PostTask(
-      BrowserThread::IO, FROM_HERE,
-      base::Bind(&CreateHangingFirstRequestInterceptorOnIO, url, url_file,
-                 prerender_start_loop.QuitClosure()));
+  CreateHangingFirstRequestInterceptor(
+      url, url_file,
+      GetIOCallbackFromUIClosure(prerender_start_loop.QuitClosure()));
   // As this load is uncommitted, it is not waited for, and hence no
   // javascript is executed.
   DisableJavascriptCalls();
   PrerenderTestURL(url, FINAL_STATUS_NAVIGATION_UNCOMMITTED, 0);
   prerender_start_loop.Run();
 
   clock->Advance(base::TimeDelta::FromSeconds(1));
   NavigateToDestURLWithDisposition(WindowOpenDisposition::CURRENT_TAB, false);
 
   PrerenderPageLoadMetricsObserver observer(GetPrerenderManager(),
@@ skipping 239 matching lines @@
   ASSERT_TRUE(content::ExecuteScriptAndExtractBool(web_contents,
                                                    "DidDisplayReallyPass()",
                                                    &display_test_result));
   ASSERT_TRUE(display_test_result);
 }
 #endif  // !defined(DISABLE_NACL)
 
 }  // namespace prerender
 
 #endif  // !defined(OS_MACOSX) || !defined(ADDRESS_SANITIZER)