[DocWriteBlocking] Add feature to block doc.written scripts if 2g-like network

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 1d8a489187bf24ba71847999558509e59898b068..f9e4e249a1deea948600756df3064258c112f77a 100644
--- a/third_party/WebKit/Source/core/loader/FrameFetchContext.cpp
+++ b/third_party/WebKit/Source/core/loader/FrameFetchContext.cpp
@@ -146,10 +146,11 @@ bool shouldDisallowFetchForMainFrameScript(const ResourceRequest& request, Fetch
     // the flag will be conveyed to the browser process only once.
     document.loader()->didObserveLoadingBehavior(WebLoadingBehaviorFlag::WebLoadingBehaviorDocumentWriteBlock);
 
-    const bool isSlowConnection = networkStateNotifier().connectionType() == WebConnectionTypeCellular2G;
-    const bool disallowFetch = document.settings()->disallowFetchForDocWrittenScriptsInMainFrame() || (document.settings()->disallowFetchForDocWrittenScriptsInMainFrameOnSlowConnections() && isSlowConnection);
+    const bool is2G = networkStateNotifier().connectionType() == WebConnectionTypeCellular2G;
+    WebEffectiveConnectionType effectiveConnection = document.frame()->loader().client()->getEffectiveConnectionType();
+    const bool is2GOrLike2G = is2G || effectiveConnection == WebEffectiveConnectionType::Type2G || effectiveConnection == WebEffectiveConnectionType::TypeSlow2G;

[Yoav Weiss, 2016/09/04 05:11:43]

Would it have been better to change the WebEffectiveConnectionType so that
Unknown is last, and we could define `<Type2G` here?

[jkarlin, 2016/09/06 11:58:45]

I don't think a strict ordering on the enum makes much sense. Connection types
will come and go over time and will be of various speeds. Once they're used by
histograms they can only be appended to.

That said, I do think a "isConnectionTypeSlow()" that uses a switch to make sure
we've addressed all of the connection types would be better.

 
-    return disallowFetch;
+    return document.settings()->disallowFetchForDocWrittenScriptsInMainFrame() || (document.settings()->disallowFetchForDocWrittenScriptsInMainFrameOnSlowConnections() && is2G) || (RuntimeEnabledFeatures::blockDocWriteIfEffectively2GEnabled() && is2GOrLike2G);
 }
 
 } // namespace