Add test runner support for overriding web_security_enabled preference.

Have TestRunner::OverridePreference() recognize "WebKitWebSecurityEnabled"
as a boolean preference which controls the web_security_enabled web
preference.

R=mkwst,jochen
BUG=254993

Review URL: https://codereview.chromium.org/601513002

Cr-Commit-Position: refs/heads/master@{#296543}

content/shell/common/test_runner/test_preferences.cc

@@ -49,6 +49,7 @@ void TestPreferences::Reset() {
   hyperlink_auditing_enabled = false;
   should_respect_image_orientation = false;
   asynchronous_spell_checking_enabled = false;
+  web_security_enabled = true;
 }
 
 }  // namespace content

content/shell/common/test_runner/test_preferences.h

@@ -43,6 +43,7 @@ struct TestPreferences {
     bool caret_browsing_enabled;
     bool should_respect_image_orientation;
     bool asynchronous_spell_checking_enabled;
+    bool web_security_enabled;
 
     TestPreferences();
     void Reset();

content/shell/common/webkit_test_helpers.cc

@@ -47,6 +47,8 @@ void ExportLayoutTestSpecificPreferences(const TestPreferences& from,
   to->allow_file_access_from_file_urls = from.allow_file_access_from_file_urls;
   to->javascript_can_open_windows_automatically =
       from.java_script_can_open_windows_automatically;
+  to->web_security_enabled =
+      from.web_security_enabled;
 }
 
 // Applies settings that differ between layout tests and regular mode. Some

content/shell/renderer/test_runner/test_runner.cc

@@ -2496,6 +2496,8 @@ void TestRunner::OverridePreference(const std::string key,
     prefs->should_respect_image_orientation = value->BooleanValue();
   } else if (key == "WebKitWebAudioEnabled") {
     DCHECK(value->BooleanValue());
+  } else if (key == "WebKitWebSecurityEnabled") {
+    prefs->web_security_enabled = value->BooleanValue();
   } else {
     std::string message("Invalid name for preference: ");
     message.append(key);