Doc.write intervention warning and error messages fixed for clarity.

third_party/WebKit/Source/core/loader/FrameFetchContext.cpp

Index: third_party/WebKit/Source/core/loader/FrameFetchContext.cpp
diff --git a/third_party/WebKit/Source/core/loader/FrameFetchContext.cpp b/third_party/WebKit/Source/core/loader/FrameFetchContext.cpp
index ec4c3918b5b848a473d496d54d795b2859fdcb07..1edc136a95f402bd64727de650785bb11ff04f66 100644
--- a/third_party/WebKit/Source/core/loader/FrameFetchContext.cpp
+++ b/third_party/WebKit/Source/core/loader/FrameFetchContext.cpp
@@ -91,9 +91,10 @@ void emitWarningForDocWriteScripts(const String& url, Document& document) {
   String message =
       "A Parser-blocking, cross site (i.e. different eTLD+1) script, " + url +
       ", is invoked via document.write. This may be blocked by "
-      "the browser if the device has poor network connectivity. "
+      "the browser due to poor network connectivity. "
       "See https://www.chromestatus.com/feature/5718547946799104 "
-      "for more details.";
+      "for more details. If the script is indeed blocked, you should see an "

[Bryan McQuade, 2017/01/18 23:47:04]

thinking about this more i'm a little concerned that devs might interpret this
last sentence as "if i don't see the subsequent error, my page isn't affected by
this issue" and they won't fix their page, so I'm inclined to omit this last "If
the script is indeed blocked..." text. We can make it clear in the linked
documentation that this message is a warning and only if you see the additional
'script was blocked' message was there an actual issue.

Given this, can we remove this last sentence?

[shivanisha, 2017/01/19 18:04:58]

I hear your concern. Omitting the last sentence might still leave users unsure
whether it actually was blocked or not, in case they do not read the link very
carefully. How about something like this:

"A Parser-blocking, cross site (i.e. different eTLD+1) script
http://ajax.cloudflare.com/cdn-cgi/nexp/dok3v=f2befc48d1/cloudflare.min.js, is
invoked via document.write. This MAY be blocked by the browser in this or a
future page load due to poor network connectivity. If blocked in this page load,
it will be confirmed in a subsequent ERROR message. See
https://www.chromestatus.com/feature/5718547946799104 for more details."

+      "error message following this.";
   document.addConsoleMessage(
       ConsoleMessage::create(JSMessageSource, WarningMessageLevel, message));
   WTFLogAlways("%s", message.utf8().data());