Timing out the HTTPS Previews URLLoader impl

When the request has been on the network for 30 seconds, the HTTPS
Preview URLLoader implementation should fallback to default behavior for
the URL hop.

Bug: 935771
Change-Id: Id76e8d116ef32d86bd7c311022723f93a6fb4c04
Reviewed-on: https://chromium-review.googlesource.com/c/1488117
Commit-Queue: Ryan Sturm <ryansturm@chromium.org>
Reviewed-by: Robert Ogden <robertogden@chromium.org>
Cr-Commit-Position: refs/heads/master@{#635733}

chrome/browser/previews/previews_lite_page_browsertest.cc

@@ -1341,8 +1341,6 @@ INSTANTIATE_TEST_SUITE_P(URLLoaderImplementation,
 
 IN_PROC_BROWSER_TEST_P(PreviewsLitePageServerTimeoutBrowserTest,
                        DISABLE_ON_WIN_MAC(LitePagePreviewsTimeout)) {
-  if (GetParam())
-    return;
   {
     // Ensure that a hung previews navigation doesn't wind up at the previews
     // server.

chrome/browser/previews/previews_lite_page_serving_url_loader.cc

@@ -9,6 +9,7 @@
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
+#include "base/location.h"
 #include "base/memory/ptr_util.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/rand_util.h"
@@ -153,10 +154,28 @@ void PreviewsLitePageServingURLLoader::StartNetworkRequest(
       mojo::MakeRequest(&network_url_loader_), frame_tree_node_id_, 0,
       network::mojom::kURLLoadOptionNone, request, std::move(client),
       net::MutableNetworkTrafficAnnotationTag(kPreviewsTrafficAnnotation));
+
+  timeout_timer_.Start(
+      FROM_HERE, previews::params::LitePagePreviewsNavigationTimeoutDuration(),
+      base::BindOnce(&PreviewsLitePageServingURLLoader::Timeout,
+                     weak_ptr_factory_.GetWeakPtr()));
 }
 
 PreviewsLitePageServingURLLoader::~PreviewsLitePageServingURLLoader() = default;
 
+void PreviewsLitePageServingURLLoader::Timeout() {
+  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
+  // If the result is already determined, don't do anything.
+  if (result_callback_.is_null())
+    return;
+
+  UMA_HISTOGRAM_ENUMERATION(
+      "Previews.ServerLitePage.ServerResponse",
+      PreviewsLitePageNavigationThrottle::ServerResponse::kTimeout);
+
+  Fallback();
+}
+
 void PreviewsLitePageServingURLLoader::Fallback() {
   DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   std::move(result_callback_)

chrome/browser/previews/previews_lite_page_serving_url_loader.h

@@ -12,6 +12,7 @@
 #include "base/memory/weak_ptr.h"
 #include "base/optional.h"
 #include "base/sequence_checker.h"
+#include "base/timer/timer.h"
 #include "content/public/browser/url_loader_request_interceptor.h"
 #include "mojo/public/cpp/bindings/binding.h"
 #include "mojo/public/cpp/system/data_pipe.h"
@@ -93,6 +94,12 @@ class PreviewsLitePageServingURLLoader
   // Calls |result_callback_| with kFallback and cleans up.
   void Fallback();
 
+  // Calls timeout if the result was not previously determined (i.e., the
+  // response has not started yet). This method is called
+  // |LitePagePreviewsNavigationTimeoutDuration()| after the network request has
+  // started.
+  void Timeout();
+
   // Sets up mojo forwarding to the navigation path. Resumes
   // |network_url_loader_| calls. Serves the start of the response to the
   // navigation path.
@@ -121,6 +128,9 @@ class PreviewsLitePageServingURLLoader
   // The previews URL that is being requested.
   GURL previews_url_;
 
+  // The timer that triggers a timeout when the request takes too long.
+  base::OneShotTimer timeout_timer_;
+
   // Forwarding client binding.
   mojo::Binding<network::mojom::URLLoader> binding_;
   network::mojom::URLLoaderClientPtr forwarding_client_;