Dev tools warning and console warning for document.write script blocking

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 f09d2ece98f445c40de0f3ebdabb3a5295bc29b7..09ed96cd82a2b674b99323ad7425bc3ec8518082 100644
--- a/third_party/WebKit/Source/core/loader/FrameFetchContext.cpp
+++ b/third_party/WebKit/Source/core/loader/FrameFetchContext.cpp
@@ -80,7 +80,14 @@ namespace blink {
 
 namespace {
 
-bool shouldDisallowFetchForMainFrameScript(const ResourceRequest& request, FetchRequest::DeferOption defer, const Document& document)
+void emitWarningForDocWriteScripts(const String& url, Document& document)
+{
+    String message = "A Parser-blocking, cross-origin script, " + url + ", is invoked via document.write. This may be blocked by the browser if the device has poor network connectivity.";
+    document.addConsoleMessage(ConsoleMessage::create(JSMessageSource, WarningMessageLevel, message));
+    WTFLogAlways("%s", message.utf8().data());
+}
+
+bool shouldDisallowFetchForMainFrameScript(const ResourceRequest& request, FetchRequest::DeferOption defer, Document& document)
 {
     // Only scripts inserted via document.write are candidates for having their
     // fetch disallowed.
@@ -115,6 +122,7 @@ bool shouldDisallowFetchForMainFrameScript(const ResourceRequest& request, Fetch
         // Recording this metric since an increase in number of reloads for pages
         // where a script was blocked could be indicative of a page break.
         document.loader()->didObserveLoadingBehavior(WebLoadingBehaviorFlag::WebLoadingBehaviorDocumentWriteBlockReload);
+        emitWarningForDocWriteScripts(request.url().getString(), document);

[jkarlin, 2016/06/23 11:20:41]

no need to have two emitWarning calls. Can just have one above the if(isReload).

[shivanisha, 2016/06/23 13:56:04]

done.

         return false;
     }
 
@@ -123,6 +131,8 @@ bool shouldDisallowFetchForMainFrameScript(const ResourceRequest& request, Fetch
     // the flag will be conveyed to the browser process only once.
     document.loader()->didObserveLoadingBehavior(WebLoadingBehaviorFlag::WebLoadingBehaviorDocumentWriteBlock);
 
+    emitWarningForDocWriteScripts(request.url().getString(), document);
+
     const bool isSlowConnection = networkStateNotifier().connectionType() == WebConnectionTypeCellular2G;
     const bool disallowFetch = document.settings()->disallowFetchForDocWrittenScriptsInMainFrame() || (document.settings()->disallowFetchForDocWrittenScriptsInMainFrameOnSlowConnections() && isSlowConnection);