Reduce canonicalization when dragging

third_party/WebKit/Source/core/editing/SelectionController.cpp

Index: third_party/WebKit/Source/core/editing/SelectionController.cpp
diff --git a/third_party/WebKit/Source/core/editing/SelectionController.cpp b/third_party/WebKit/Source/core/editing/SelectionController.cpp
index b53e47fc7df02c2823e0edb3b917245e9d536d6d..c253d60a8b364671d45f1bfe5f988ce3df32485e 100644
--- a/third_party/WebKit/Source/core/editing/SelectionController.cpp
+++ b/third_party/WebKit/Source/core/editing/SelectionController.cpp
@@ -387,6 +387,9 @@ void SelectionController::updateSelectionForMouseDrag(
   } else {
     basePosition = selection().computeVisibleSelectionInFlatTree().base();
   }
+  if (basePosition.isNull())
+    return;
+
   const SelectionInFlatTree& appliedSelection = applySelectAll(
       basePosition, targetPosition.deepEquivalent(), mousePressNode,
       dragStartPos, target, hitTestResult.localPoint());