Make SelectionController to call TextDistance() with proper range

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

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights
  * reserved.
  * Copyright (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2012 Digia Plc. and/or its subsidiary(-ies)
  * Copyright (C) 2015 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
@@ skipping 197 matching lines @@
     SelectionInFlatTree::Builder builder;
     builder.SetGranularity(this->Selection().Granularity());
     if (frame_->GetEditor().Behavior().ShouldConsiderSelectionAsDirectional()) {
       builder.SetBaseAndExtent(selection.Base(), pos);
     } else if (pos.IsNull()) {
       builder.SetBaseAndExtent(selection.Base(), selection.Extent());
     } else {
       // Shift+Click deselects when selection was created right-to-left
       const PositionInFlatTree& start = selection.Start();
       const PositionInFlatTree& end = selection.end();
-      const int distance_to_start = TextDistance(start, pos);
-      const int distance_to_end = TextDistance(pos, end);
-      builder.SetBaseAndExtent(
-          distance_to_start <= distance_to_end ? end : start, pos);
+      if (pos < start) {
+        // |distance_to_start < distance_to_end|.
+        builder.SetBaseAndExtent(end, pos);
+      } else if (end < pos) {
+        // |distance_to_start > distance_to_end|.
+        builder.SetBaseAndExtent(start, pos);
+      } else {
+        const int distance_to_start = TextDistance(start, pos);
+        const int distance_to_end = TextDistance(pos, end);
+        builder.SetBaseAndExtent(
+            distance_to_start <= distance_to_end ? end : start, pos);
+      }
     }
 
     UpdateSelectionForMouseDownDispatchingSelectStart(
         inner_node, CreateVisibleSelection(builder.Build()),
         this->Selection().Granularity(), HandleVisibility::kNotVisible);
     return false;
   }
 
   if (selection_state_ == SelectionState::kExtendedSelection) {
     UpdateSelectionForMouseDownDispatchingSelectStart(
@@ skipping 902 matching lines @@
 
 bool IsExtendingSelection(const MouseEventWithHitTestResults& event) {
   bool is_mouse_down_on_link_or_image =
       event.IsOverLink() || event.GetHitTestResult().GetImage();
   return (event.Event().GetModifiers() & WebInputEvent::Modifiers::kShiftKey) !=
              0 &&
          !is_mouse_down_on_link_or_image;
 }
 
 }  // namespace blink