First-cut at fixing unhandled Tap event returns in Blink.

Source/core/page/EventHandler.cpp

Index: Source/core/page/EventHandler.cpp
diff --git a/Source/core/page/EventHandler.cpp b/Source/core/page/EventHandler.cpp
index 55a07108fe384eddf4e7d7407552417884a1d2ed..fcc9e4f8cc6f7e80071cffa1057b150e56639c86 100644
--- a/Source/core/page/EventHandler.cpp
+++ b/Source/core/page/EventHandler.cpp
@@ -538,8 +538,9 @@ bool EventHandler::handleMousePressEventSingleClick(const MouseEventWithHitTestR
         newSelection = expandSelectionToRespectUserSelectAll(innerNode, VisibleSelection(visiblePos));
     }
 
-    bool handled = updateSelectionForMouseDownDispatchingSelectStart(innerNode, newSelection, granularity);
-    return handled;
+    // Updating the selection is considered side-effect of the event and so it doesn't impact the handled state.
+    updateSelectionForMouseDownDispatchingSelectStart(innerNode, newSelection, granularity);
+    return false;
 }
 
 static inline bool canMouseDownStartSelect(Node* node)