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

third_party/WebKit/Source/core/frame/Settings.in

Index: third_party/WebKit/Source/core/frame/Settings.in
diff --git a/third_party/WebKit/Source/core/frame/Settings.in b/third_party/WebKit/Source/core/frame/Settings.in
index 69f1dbd0d5fd9d2771b719bfaee516d369b60838..37d265d48aa47e27c2f5b42517b7be70ce57cd2d 100644
--- a/third_party/WebKit/Source/core/frame/Settings.in
+++ b/third_party/WebKit/Source/core/frame/Settings.in
@@ -382,7 +382,11 @@ fetchIncreaseAsyncScriptPriority initial=false
 fetchIncreasePriorities initial=false
 
 # Whether to disallow network fetches for parser blocking scripts in the main
-# frame inserted via document.write.
+# frame inserted via document.write, for users on slow connections.
+disallowFetchForDocWrittenScriptsInMainFrameOnSlowConnections initial=false
+
+# Whether to disallow network fetches for parser blocking scripts in the main
+# frame inserted via document.write, regardless of connection type.
 disallowFetchForDocWrittenScriptsInMainFrame initial=false
 
 # The autoplay gesture override experiment is described in crbug.com/487345 .