[webui][ntp] Enable process-per-site

Process-per-site makes all WebUI NTPs share a single renderer process.
This is what the local NTP does and has the following performance
advantages (measured on my linux machine):

* Reduces mean of NewTabPage.LoadTime.WebUINTP (duration from starting
  the NTP navigation until the most visited items are added to the DOM)
  from 271ms to 141ms.

* Reduces memory overhead of opening a new NTP from ~30MB to ~5MB.

NOTE: The aforementioned performance improvements only hold true if
another NTP is open to have the process pre-warmed. The WebUI NTP does
not seem to use the pre-warmed spare renderer.

+ Move existing WebUI NTP browser test to //c/b/ui/webui/new_tab_page.

Bug: 1075641
Change-Id: Id94294eac41e3ab083e8eece567941ef4d40d08b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2220634
Commit-Queue: Tibor Goldschwendt <tiborg@chromium.org>
Auto-Submit: Tibor Goldschwendt <tiborg@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
Reviewed-by: Alex Moshchuk <alexmos@chromium.org>
Cr-Commit-Position: refs/heads/master@{#773865}

chrome/browser/chrome_content_browser_client.cc

@@ -1604,8 +1604,10 @@ bool ChromeContentBrowserClient::ShouldUseProcessPerSite(
 
   // NTP should use process-per-site.  This is a performance optimization to
   // reduce process count associated with NTP tabs.
-  if (site_url == GURL(chrome::kChromeUINewTabURL))
+  if (site_url == GURL(chrome::kChromeUINewTabURL) ||
+      site_url == GURL(chrome::kChromeUINewTabPageURL)) {
     return true;
+  }
 
   // The web footer experiment should share its renderer to not effectively
   // instantiate one per window. See https://crbug.com/993502.

chrome/browser/search/ntp_navigation_browsertest.cc

@@ -12,8 +12,6 @@
 #include "content/public/test/browser_test.h"
 #include "net/dns/mock_host_resolver.h"
 
-#include "chrome/browser/search/ntp_features.h"
-
 class NtpNavigationBrowserTest : public InProcessBrowserTest {
  public:
   NtpNavigationBrowserTest() = default;
@@ -43,30 +41,3 @@ IN_PROC_BROWSER_TEST_F(NtpNavigationBrowserTest, VerifyNtpSiteInstance) {
   ASSERT_EQ(local_ntp_url,
             web_contents->GetMainFrame()->GetSiteInstance()->GetSiteURL());
 }
-
-// Subclass to allow running tests against the WebUI NTP implementation.
-class WebUiNtpNavigationBrowserTest : public NtpNavigationBrowserTest {
- public:
-  WebUiNtpNavigationBrowserTest() {
-    feature_list_.InitAndEnableFeature(ntp_features::kWebUI);
-  }
-  ~WebUiNtpNavigationBrowserTest() override = default;
-
- private:
-  base::test::ScopedFeatureList feature_list_;
-};
-
-// Verify that the WebUI NTP commits in a SiteInstance with the WebUI URL.
-IN_PROC_BROWSER_TEST_F(WebUiNtpNavigationBrowserTest,
-                       VerifyWebUiNtpSiteInstance) {
-  GURL ntp_url(chrome::kChromeUINewTabURL);
-  ui_test_utils::NavigateToURL(browser(), ntp_url);
-
-  content::WebContents* web_contents =
-      browser()->tab_strip_model()->GetActiveWebContents();
-  ASSERT_EQ(ntp_url, web_contents->GetLastCommittedURL());
-
-  GURL webui_ntp_url(chrome::kChromeUINewTabPageURL);
-  ASSERT_EQ(webui_ntp_url,
-            web_contents->GetMainFrame()->GetSiteInstance()->GetSiteURL());
-}

chrome/browser/ui/webui/new_tab_page/webui_ntp_browsertest.cc

+// Copyright 2020 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 "chrome/browser/search/ntp_features.h"
+#include "chrome/browser/ui/browser.h"
+#include "chrome/browser/ui/browser_commands.h"
+#include "chrome/common/webui_url_constants.h"
+#include "chrome/test/base/in_process_browser_test.h"
+#include "chrome/test/base/ui_test_utils.h"
+#include "content/public/browser/web_contents.h"
+#include "content/public/test/browser_test.h"
+#include "content/public/test/browser_test_utils.h"
+#include "net/dns/mock_host_resolver.h"
+
+class WebUiNtpBrowserTest : public InProcessBrowserTest {
+ public:
+  WebUiNtpBrowserTest() {
+    feature_list_.InitAndEnableFeature(ntp_features::kWebUI);
+  }
+  ~WebUiNtpBrowserTest() override = default;
+
+  void SetUpCommandLine(base::CommandLine* command_line) override {
+    embedded_test_server()->ServeFilesFromSourceDirectory("content/test/data");
+    ASSERT_TRUE(embedded_test_server()->InitializeAndListen());
+  }
+
+  void SetUpOnMainThread() override {
+    host_resolver()->AddRule("*", "127.0.0.1");
+    embedded_test_server()->StartAcceptingConnections();
+  }
+
+ private:
+  base::test::ScopedFeatureList feature_list_;
+};
+
+// Verify that the WebUI NTP commits in a SiteInstance with the WebUI URL.
+IN_PROC_BROWSER_TEST_F(WebUiNtpBrowserTest, VerifyWebUiNtpSiteInstance) {
+  GURL ntp_url(chrome::kChromeUINewTabURL);
+  ui_test_utils::NavigateToURL(browser(), ntp_url);
+
+  content::WebContents* web_contents =
+      browser()->tab_strip_model()->GetActiveWebContents();
+  ASSERT_EQ(ntp_url, web_contents->GetLastCommittedURL());
+
+  GURL webui_ntp_url(chrome::kChromeUINewTabPageURL);
+  ASSERT_EQ(webui_ntp_url,
+            web_contents->GetMainFrame()->GetSiteInstance()->GetSiteURL());
+}
+
+// Verify that the WebUI NTP uses process-per-site.
+IN_PROC_BROWSER_TEST_F(WebUiNtpBrowserTest, ProcessPerSite) {
+  std::vector<content::WebContents*> tabs;
+
+  // Open a few NTPs.
+  for (size_t i = 0; i < 3; i++) {
+    content::WebContentsAddedObserver tab_observer;
+    chrome::NewTab(browser());
+
+    // Wait for the new tab.
+    auto* tab = tab_observer.GetWebContents();
+    ASSERT_TRUE(WaitForLoadStop(tab));
+
+    // Sanity check: the NTP should be a WebUI NTP (and not chrome://newtab/ or
+    // some other NTP).
+    EXPECT_EQ(GURL(chrome::kChromeUINewTabPageURL).spec(),
+              EvalJs(tab, "window.location.href",
+                     content::EXECUTE_SCRIPT_DEFAULT_OPTIONS,
+                     /*world_id=*/1));
+
+    tabs.push_back(tab);
+  }
+
+  // Verify that all NTPs share a process.
+  for (size_t i = 1; i < tabs.size(); i++) {
+    EXPECT_EQ(tabs[0]->GetMainFrame()->GetProcess(),
+              tabs[i]->GetMainFrame()->GetProcess());
+  }
+}

chrome/test/BUILD.gn

@@ -1345,6 +1345,7 @@ if (!is_android) {
       "../browser/ui/webui/management_ui_browsertest.cc",
       "../browser/ui/webui/net_internals/net_internals_ui_browsertest.cc",
       "../browser/ui/webui/net_internals/net_internals_ui_browsertest.h",
+      "../browser/ui/webui/new_tab_page/webui_ntp_browsertest.cc",
       "../browser/ui/webui/ntp/new_tab_ui_browsertest.cc",
       "../browser/ui/webui/policy_ui_browsertest.cc",
       "../browser/ui/webui/prefs_internals_browsertest.cc",