NTP: load chrome://newtab on NTP tabs when DSE changes

When the default search engine is changed, chrome://newtab is loaded on
the tabs with a NTP loaded. chrome://newtab will redirect to the NTP
associated with the new default search engine.

Bug: 1129499
Change-Id: I03360bb781c7bf94e2db65f282ee163386dd26cc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2423169Reviewed-by: Tibor Goldschwendt <tiborg@chromium.org>
Commit-Queue: Esmael Elmoslimany <aee@chromium.org>
Cr-Commit-Position: refs/heads/master@{#809479}

chrome/browser/ui/browser_instant_controller.cc

@@ -91,11 +91,6 @@ BrowserInstantController::~BrowserInstantController() = default;
 
 void BrowserInstantController::OnSearchEngineBaseURLChanged(
     SearchEngineBaseURLTracker::ChangeReason change_reason) {
-  InstantService* instant_service =
-      InstantServiceFactory::GetForProfile(profile());
-  if (!instant_service)
-    return;
-
   TabStripModel* tab_model = browser_->tab_strip_model();
   int count = tab_model->count();
   for (int index = 0; index < count; ++index) {
@@ -103,29 +98,32 @@ void BrowserInstantController::OnSearchEngineBaseURLChanged(
     if (!contents)
       continue;
 
+    bool is_ntp = contents->GetMainFrame()->GetSiteInstance()->GetSiteURL() ==
+                  GURL(chrome::kChromeUINewTabPageURL);
+
+    if (!is_ntp) {
+      InstantService* instant_service =
+          InstantServiceFactory::GetForProfile(profile());
+      if (instant_service) {
         // Send the new NTP URL to the renderer.
-    content::RenderProcessHost* rph = contents->GetMainFrame()->GetProcess();
+        content::RenderProcessHost* rph =
+            contents->GetMainFrame()->GetProcess();
         instant_service->SendNewTabPageURLToRenderer(rph);
+        is_ntp = instant_service->IsInstantProcess(rph->GetID());
+      }
+    }
 
-    if (!instant_service->IsInstantProcess(rph->GetID()))
+    if (!is_ntp)
       continue;
 
-    bool google_base_url_domain_changed =
-        change_reason ==
-        SearchEngineBaseURLTracker::ChangeReason::GOOGLE_BASE_URL;
-    if (google_base_url_domain_changed) {
-      GURL local_ntp_url(chrome::kChromeSearchLocalNtpUrl);
-      // Replace the server NTP with the local NTP (or reload the local NTP).
-      content::NavigationController::LoadURLParams params(local_ntp_url);
+    // When default search engine is changed navigate to chrome://newtab which
+    // will redirect to the new tab page associated with the search engine.
+    GURL url(chrome::kChromeUINewTabURL);
+    content::NavigationController::LoadURLParams params(url);
     params.should_replace_current_entry = true;
     params.referrer = content::Referrer();
     params.transition_type = ui::PAGE_TRANSITION_RELOAD;
     contents->GetController().LoadURLWithParams(params);
-    } else {
-      // Reload the contents to ensure that it gets assigned to a
-      // non-privileged renderer.
-      TabReloader::Reload(contents);
-    }
   }
 }
 

chrome/browser/ui/browser_instant_controller_unittest.cc

@@ -39,17 +39,16 @@ struct TabReloadTestCase {
   const char* description;
   const char* start_url;
   bool start_in_instant_process;
-  bool should_reload;
-  bool end_in_local_ntp;
-  bool end_in_instant_process;
+  bool end_in_ntp;
 };
 
 // Test cases for when Google is the initial, but not final provider.
 const TabReloadTestCase kTabReloadTestCasesFinalProviderNotGoogle[] = {
-    {"Local NTP", chrome::kChromeSearchLocalNtpUrl, true, true, true, true},
-    {"Remote SERP", "https://www.google.com/url?bar=search+terms", false, false,
-     false, false},
-    {"Other NTP", "https://bar.com/newtab", false, false, false, false}};
+    {"Local NTP", chrome::kChromeSearchLocalNtpUrl, true, true},
+    {"NTP", chrome::kChromeUINewTabPageURL, false, true},
+    {"Remote SERP", "https://www.google.com/url?bar=search+terms", false,
+     false},
+    {"Other NTP", "https://bar.com/newtab", false, false}};
 
 class FakeWebContentsObserver : public content::WebContentsObserver {
  public:
@@ -121,14 +120,6 @@ TEST_F(BrowserInstantControllerTest, DefaultSearchProviderChanged) {
     const TabReloadTestCase& test =
         kTabReloadTestCasesFinalProviderNotGoogle[i];
 
-    if (test.should_reload) {
-      // Validate final instant state.
-      EXPECT_EQ(test.end_in_instant_process,
-                search::ShouldAssignURLToInstantRenderer(
-                    observer->current_url(), profile()))
-          << test.description;
-    }
-
     // Ensure only the expected tabs(contents) reloaded.
     // RunUntilIdle() ensures that tasks posted by TabReloader::Reload run.
     base::RunLoop().RunUntilIdle();
@@ -138,14 +129,8 @@ TEST_F(BrowserInstantControllerTest, DefaultSearchProviderChanged) {
       observer->WaitForNavigationStart();
     }
 
-    // WaitForLoadStop ensures that all relevant navigation callbacks caused by
-    // TabReloader::Run complete.
-    // content::WaitForLoadStop(observer->web_contents());
-    EXPECT_EQ(test.should_reload ? 1 : 0, observer->num_reloads())
-        << test.description;
-
-    if (test.end_in_local_ntp) {
-      EXPECT_EQ(GURL(chrome::kChromeSearchLocalNtpUrl), observer->current_url())
+    if (test.end_in_ntp) {
+      EXPECT_EQ(GURL(chrome::kChromeUINewTabURL), observer->current_url())
           << test.description;
     }
   }