http://trac.webkit.org/changeset/146534 has likely caused Chromium Linux x64 perf regression: http://build.chromium.org/p/chromium/builders/Linux%20x64/builds/47214 WebKit changes rolled in https://src.chromium.org/viewvc/chrome?view=rev&revision=189758 are: http://trac.webkit.org/log/?rev=146554&stop_rev=146526&verbose=o
Created another bug to track this https://bugs.webkit.org/show_bug.cgi?id=113017 *** This bug has been marked as a duplicate of bug 113017 ***