Add about:flags support for doc.write script blocking.

chrome/browser/about_flags.cc

Index: chrome/browser/about_flags.cc
diff --git a/chrome/browser/about_flags.cc b/chrome/browser/about_flags.cc
index c38033605b76f76f6ecd93d565b5361624c4fdb2..6a6b3872ef68e4517ccd1e6d415a1383b30492fe 100644
--- a/chrome/browser/about_flags.cc
+++ b/chrome/browser/about_flags.cc
@@ -1587,13 +1587,15 @@ const FeatureEntry kFeatureEntries[] = {
      IDS_FLAGS_OFFLINE_PAGES_BACKGROUND_LOADING_DESCRIPTION, kOsAndroid,
      FEATURE_VALUE_TYPE(offline_pages::kOfflinePagesBackgroundLoadingFeature)},
 #endif  // defined(OS_ANDROID)
-    {"low-priority-iframes", IDS_FLAGS_LOW_PRIORITY_IFRAMES_UI_NAME,
-     IDS_FLAGS_LOW_PRIORITY_IFRAMES_UI_DESCRIPTION, kOsAll,
+    {"disallow-doc-written-script-loads",
+     IDS_FLAGS_DISALLOW_DOC_WRITTEN_SCRIPTS_UI_NAME,
+     IDS_FLAGS_DISALLOW_DOC_WRITTEN_SCRIPTS_UI_DESCRIPTION, kOsAll,
      // NOTE: if we want to add additional experiment entries for other
      // features controlled by kBlinkSettings, we'll need to add logic to
      // merge the flag values.
-     SINGLE_VALUE_TYPE_AND_VALUE(switches::kBlinkSettings,
-                                 "lowPriorityIframes=true")},
+     SINGLE_VALUE_TYPE_AND_VALUE(
+         switches::kBlinkSettings,
+         "disallowFetchForDocWrittenScriptsInMainFrame=true")},
 #if defined(OS_ANDROID)
     {"enable-ntp-popular-sites", IDS_FLAGS_NTP_POPULAR_SITES_NAME,
      IDS_FLAGS_NTP_POPULAR_SITES_DESCRIPTION, kOsAndroid,