RenderLayer::hitTest currently has quirk where it pretends the layer was hit even if it was not, in case it is the top layer and the mouse-button is down, or just released. This code is used to ensure the origin frame of a drag-operation accepts the event that is routed to it, and to ensure that hit-tests on a frame-view scroll bar (which are not hit-tested!) hits the document. The first reason is unnecessary, since the EventHandler would already know that it is capturing drag events and not forwarding them to a deeper frame, and the second reason should be replaced with a more accurate test actually testing if the frameview scroll bar was hit (if participates in hit testing).
Created attachment 164372 [details] Patch
Comment on attachment 164372 [details] Patch Attachment 164372 [details] did not pass chromium-ews (chromium-xvfb): Output: http://queues.webkit.org/results/13864671 New failing tests: touchadjustment/touch-links-longpress.html WebFrameTest.SelectRange fast/dom/shadow/selections-in-shadow.html
Comment on attachment 164372 [details] Patch Clearing review. The patch was not fully handling selection by mouse-drag.