SafeBrowsing: Add SBErrorDisplayOptions.always_show_back_to_safety

Adding this option allows UI to set the visibility of the
'Back to safety' button.

Webview: Set to false, so the button would only be shown where
there is a page to go back to.
Chromium: option is always set to true so always show the
Back to safety button. Where there is no previous page,
the user is taken to the new tab page.

Bug: 760383
Change-Id: I8857b6bf2ff977c572f507f817bf815307453c13
Reviewed-on: https://chromium-review.googlesource.com/641435Reviewed-by: Jialiu Lin <jialiul@chromium.org>
Reviewed-by: Adrienne Porter Felt <felt@chromium.org>
Reviewed-by: Selim Gurun <sgurun@chromium.org>
Reviewed-by: Nate Fischer <ntfschr@chromium.org>
Commit-Queue: Edward Jung <edwardjung@chromium.org>
Cr-Commit-Position: refs/heads/master@{#501227}

android_webview/browser/aw_safe_browsing_blocking_page.cc

@@ -98,6 +98,7 @@ void AwSafeBrowsingBlockingPage::ShowBlockingPage(
             pref_service->GetBoolean(
                 ::prefs::kSafeBrowsingProceedAnywayDisabled),
             false,                    // should_open_links_in_new_tab
+            false,                    // always_show_back_to_safety
             "cpn_safe_browsing_wv");  // help_center_article_link
 
     ErrorUiType errorType =

chrome/browser/safe_browsing/safe_browsing_blocking_page.cc

@@ -79,6 +79,7 @@ class SafeBrowsingBlockingPageFactoryImpl
         IsExtendedReportingEnabled(*prefs), IsScout(*prefs),
         is_proceed_anyway_disabled,
         true,  // should_open_links_in_new_tab
+        true,  // always_show_back_to_safety
         kHelpCenterLink);
 
     return new SafeBrowsingBlockingPage(ui_manager, web_contents,

chrome/browser/safe_browsing/safe_browsing_blocking_page_test.cc

@@ -329,6 +329,7 @@ class TestSafeBrowsingBlockingPageFactory
         IsExtendedReportingEnabled(*prefs), IsScout(*prefs),
         is_proceed_anyway_disabled,
         true,   // should_open_links_in_new_tab
+        false,  // check_can_go_back_to_safety
         "cpn_safe_browsing" /* help_center_article_link */);
     return new TestSafeBrowsingBlockingPage(delegate, web_contents,
                                             main_frame_url, unsafe_resources,

chrome/browser/safe_browsing/safe_browsing_blocking_page_unittest.cc

@@ -95,6 +95,7 @@ class TestSafeBrowsingBlockingPageFactory
         IsExtendedReportingEnabled(*prefs), IsScout(*prefs),
         is_proceed_anyway_disabled,
         true,  // should_open_links_in_new_tab
+        true,  // always_show_back_to_safety
         "cpn_safe_browsing" /* help_center_article_link */);
     return new TestSafeBrowsingBlockingPage(manager, web_contents,
                                             main_frame_url, unsafe_resources,
@@ -177,6 +178,7 @@ class TestSafeBrowsingBlockingQuietPageFactory
         IsExtendedReportingEnabled(*prefs), IsScout(*prefs),
         is_proceed_anyway_disabled,
         true,  // should_open_links_in_new_tab
+        true,  // always_show_back_to_safety
         "cpn_safe_browsing" /* help_center_article_link */);
     return new TestSafeBrowsingBlockingPageQuiet(
         manager, web_contents, main_frame_url, unsafe_resources,

chrome/browser/safe_browsing/ui_manager_unittest.cc

@@ -437,6 +437,7 @@ class TestSafeBrowsingBlockingPage : public SafeBrowsingBlockingPage {
                 false,                   // is_scout_reporting_enabled
                 false,                   // is_proceed_anyway_disabled
                 true,                    // should_open_links_in_new_tab
+                true,                    // always_show_back_to_safety
                 "cpn_safe_browsing")) {  // help_center_article_link
     // Don't delay details at all for the unittest.
     SetThreatDetailsProceedDelayForTesting(0);

components/safe_browsing/base_blocking_page.cc

@@ -80,6 +80,7 @@ BaseBlockingPage::CreateDefaultDisplayOptions(
       false,                 // is_scout
       false,                 // kSafeBrowsingProceedAnywayDisabled
       false,                 // should_open_links_in_new_tab
+      true,                  // always_show_back_to_safety
       "cpn_safe_browsing");  // help_center_article_link
 }
 

components/safe_browsing/triggers/trigger_manager.cc

@@ -84,6 +84,7 @@ SBErrorOptions TriggerManager::GetSBErrorDisplayOptions(
                         IsScout(pref_service),
                         /*is_proceed_anyway_disabled=*/false,
                         /*should_open_links_in_new_tab=*/false,
+                        /*show_back_to_safety_button=*/true,
                         /*help_center_article_link=*/std::string());
 }
 

components/security_interstitials/core/base_safe_browsing_error_ui.cc

@@ -32,6 +32,7 @@ BaseSafeBrowsingErrorUI::SBErrorDisplayOptions::SBErrorDisplayOptions(
     bool is_scout_reporting_enabled,
     bool is_proceed_anyway_disabled,
     bool should_open_links_in_new_tab,
+    bool always_show_back_to_safety,
     const std::string& help_center_article_link)
     : is_main_frame_load_blocked(is_main_frame_load_blocked),
       is_extended_reporting_opt_in_allowed(
@@ -41,6 +42,7 @@ BaseSafeBrowsingErrorUI::SBErrorDisplayOptions::SBErrorDisplayOptions(
       is_scout_reporting_enabled(is_scout_reporting_enabled),
       is_proceed_anyway_disabled(is_proceed_anyway_disabled),
       should_open_links_in_new_tab(should_open_links_in_new_tab),
+      always_show_back_to_safety(always_show_back_to_safety),
       help_center_article_link(help_center_article_link) {}
 
 BaseSafeBrowsingErrorUI::SBErrorDisplayOptions::SBErrorDisplayOptions(
@@ -53,6 +55,7 @@ BaseSafeBrowsingErrorUI::SBErrorDisplayOptions::SBErrorDisplayOptions(
       is_scout_reporting_enabled(other.is_scout_reporting_enabled),
       is_proceed_anyway_disabled(other.is_proceed_anyway_disabled),
       should_open_links_in_new_tab(other.should_open_links_in_new_tab),
+      always_show_back_to_safety(other.always_show_back_to_safety),
       help_center_article_link(other.help_center_article_link) {}
 
 }  // security_interstitials

components/security_interstitials/core/base_safe_browsing_error_ui.h

@@ -33,6 +33,7 @@ class BaseSafeBrowsingErrorUI {
                           bool is_scout_reporting_enabled,
                           bool is_proceed_anyway_disabled,
                           bool should_open_links_in_new_tab,
+                          bool always_show_back_to_safety,
                           const std::string& help_center_article_link);
 
     SBErrorDisplayOptions(const SBErrorDisplayOptions& other);
@@ -64,6 +65,12 @@ class BaseSafeBrowsingErrorUI {
     // Indicates if links should use a new foreground tab or the current tab.
     bool should_open_links_in_new_tab;
 
+    // Indicates if the 'Back to safety' primary action button should always be
+    // shown. If the option is false, this button is shown only when there is
+    // a proper page to navigate back to. Chrome and Chromium builds should
+    // always set this option to true,
+    bool always_show_back_to_safety;
+
     // The p= query parameter used when visiting the Help Center. If this is
     // nullptr, then a default value will be used for the SafeBrowsing article.
     std::string help_center_article_link;
@@ -109,6 +116,10 @@ class BaseSafeBrowsingErrorUI {
     return display_options_.should_open_links_in_new_tab;
   }
 
+  bool always_show_back_to_safety() const {
+    return display_options_.always_show_back_to_safety;
+  }
+
   const std::string& get_help_center_article_link() const {
     return display_options_.help_center_article_link;
   }

components/security_interstitials/core/safe_browsing_loud_error_ui.cc

@@ -94,7 +94,10 @@ void SafeBrowsingLoudErrorUI::PopulateStringsForHtml(
       "primaryButtonText",
       l10n_util::GetStringUTF16(IDS_SAFEBROWSING_OVERRIDABLE_SAFETY_BUTTON));
   load_time_data->SetBoolean("overridable", !is_proceed_anyway_disabled());
-  load_time_data->SetBoolean("hide_primary_button", !controller()->CanGoBack());
+
+  load_time_data->SetBoolean(
+      "hide_primary_button",
+      always_show_back_to_safety() ? false : !controller()->CanGoBack());
 
   switch (interstitial_reason()) {
     case BaseSafeBrowsingErrorUI::SB_REASON_MALWARE: