Lower the priority of iframes in the browser

Previous CL did for frames and requests that start from Blink.
This CL additionally does it for frames or requests that
start in the browser.

Bug: 800035
Change-Id: Id31dafa267a54971aa175077b017f5ee26d20d44
Reviewed-on: https://chromium-review.googlesource.com/922886
Commit-Queue: Tarun Bansal <tbansal@chromium.org>
Reviewed-by: Charlie Harrison <csharrison@chromium.org>
Cr-Commit-Position: refs/heads/master@{#537539}

content/browser/loader/navigation_url_loader_network_service.cc

@@ -8,6 +8,7 @@
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
+#include "base/feature_list.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/task_scheduler/post_task.h"
 #include "base/trace_event/trace_event.h"
@@ -198,7 +199,14 @@ std::unique_ptr<network::ResourceRequest> CreateResourceRequest(
   new_request->method = request_info->common_params.method;
   new_request->url = request_info->common_params.url;
   new_request->site_for_cookies = request_info->site_for_cookies;
-  new_request->priority = net::HIGHEST;
+
+  net::RequestPriority net_priority = net::HIGHEST;
+  if (!request_info->is_main_frame &&
+      base::FeatureList::IsEnabled(features::kLowPriorityIframes)) {
+    net_priority = net::LOWEST;
+  }
+  new_request->priority = net_priority;
+
   new_request->render_frame_id = frame_tree_node_id;
 
   // The code below to set fields like request_initiator, referrer, etc has

content/browser/loader/navigation_url_loader_network_service_unittest.cc

@@ -16,6 +16,7 @@
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/navigation_ui_data.h"
 #include "content/public/browser/storage_partition.h"
+#include "content/public/common/content_features.h"
 #include "content/public/common/content_switches.h"
 #include "content/public/common/service_manager_connection.h"
 #include "content/public/test/test_browser_context.h"
@@ -129,7 +130,8 @@ class NavigationURLLoaderNetworkServiceTest : public testing::Test {
       const std::string& headers,
       const std::string& method,
       NavigationURLLoaderDelegate* delegate,
-      bool allow_download = false) {
+      bool allow_download = false,
+      bool is_main_frame = true) {
     mojom::BeginNavigationParamsPtr begin_params =
         mojom::BeginNavigationParams::New(
             headers, net::LOAD_NORMAL, false /* skip_service_worker */,
@@ -147,11 +149,10 @@ class NavigationURLLoaderNetworkServiceTest : public testing::Test {
 
     std::unique_ptr<NavigationRequestInfo> request_info(
         new NavigationRequestInfo(
-            common_params, std::move(begin_params), url,
-            true /* is_main_frame */, false /* parent_is_main_frame */,
-            false /* are_ancestors_secure */, -1 /* frame_tree_node_id */,
-            false /* is_for_guests_only */, false /* report_raw_headers */,
-            false /* is_prerenering */));
+            common_params, std::move(begin_params), url, is_main_frame,
+            false /* parent_is_main_frame */, false /* are_ancestors_secure */,
+            -1 /* frame_tree_node_id */, false /* is_for_guests_only */,
+            false /* report_raw_headers */, false /* is_prerenering */));
     std::vector<std::unique_ptr<URLLoaderRequestHandler>> handlers;
     most_recent_resource_request_ = base::nullopt;
     handlers.push_back(std::make_unique<TestURLLoaderRequestHandler>(
@@ -212,6 +213,25 @@ class NavigationURLLoaderNetworkServiceTest : public testing::Test {
     }
   }
 
+  net::RequestPriority NavigateAndReturnRequestPriority(const GURL& url,
+                                                        bool is_main_frame) {
+    TestNavigationURLLoaderDelegate delegate;
+    base::test::ScopedFeatureList scoped_feature_list_;
+
+    scoped_feature_list_.InitAndEnableFeature(features::kLowPriorityIframes);
+
+    std::unique_ptr<NavigationURLLoader> loader = CreateTestLoader(
+        url,
+        base::StringPrintf("%s: %s", net::HttpRequestHeaders::kOrigin,
+                           url.GetOrigin().spec().c_str()),
+        "GET", &delegate, false /* allow_download */, is_main_frame);
+    delegate.WaitForRequestRedirected();
+    loader->FollowRedirect();
+    delegate.WaitForResponseStarted();
+
+    return most_recent_resource_request_.value().priority;
+  }
+
  protected:
   base::test::ScopedFeatureList feature_list_;
   TestBrowserThreadBundle thread_bundle_;
@@ -220,6 +240,16 @@ class NavigationURLLoaderNetworkServiceTest : public testing::Test {
   base::Optional<network::ResourceRequest> most_recent_resource_request_;
 };
 
+TEST_F(NavigationURLLoaderNetworkServiceTest, RequestPriority) {
+  ASSERT_TRUE(http_test_server_.Start());
+  const GURL url = http_test_server_.GetURL("/redirect301-to-echo");
+
+  EXPECT_EQ(net::HIGHEST,
+            NavigateAndReturnRequestPriority(url, true /* is_main_frame */));
+  EXPECT_EQ(net::LOWEST,
+            NavigateAndReturnRequestPriority(url, false /* is_main_frame */));
+}
+
 TEST_F(NavigationURLLoaderNetworkServiceTest, Redirect301Tests) {
   ASSERT_TRUE(http_test_server_.Start());
 

content/browser/loader/resource_dispatcher_host_impl.cc

@@ -1894,8 +1894,13 @@ void ResourceDispatcherHostImpl::BeginNavigationRequest(
   DCHECK(!(load_flags & net::LOAD_IGNORE_LIMITS));
 
   std::unique_ptr<net::URLRequest> new_request;
+  net::RequestPriority net_priority = net::HIGHEST;
+  if (!info.is_main_frame &&
+      base::FeatureList::IsEnabled(features::kLowPriorityIframes)) {
+    net_priority = net::LOWEST;
+  }
   new_request = request_context->CreateRequest(
-      info.common_params.url, net::HIGHEST, nullptr, GetTrafficAnnotation());
+      info.common_params.url, net_priority, nullptr, GetTrafficAnnotation());
 
   new_request->set_method(info.common_params.method);
   new_request->set_site_for_cookies(info.site_for_cookies);