Do not send redundant selectionchange-events (decouple focus)

third_party/WebKit/Source/core/dom/Element.cpp

Index: third_party/WebKit/Source/core/dom/Element.cpp
diff --git a/third_party/WebKit/Source/core/dom/Element.cpp b/third_party/WebKit/Source/core/dom/Element.cpp
index 2fde2c526802721659102806ad693fc66f3f70b6..147bb266e0eb3a1a14c019ff5615d12fa7ac44fa 100644
--- a/third_party/WebKit/Source/core/dom/Element.cpp
+++ b/third_party/WebKit/Source/core/dom/Element.cpp
@@ -2681,8 +2681,9 @@ void Element::updateFocusAppearance(
     SelectionBehaviorOnFocus selectionBehavior) {
   if (selectionBehavior == SelectionBehaviorOnFocus::None)
     return;
+
+  LocalFrame* frame = document().frame();

[yosin_UTC9, 2017/02/09 13:02:17]

We can early return here if |!frame|.
Let's hoist |if (!frame)| at L2687 here.

   if (isRootEditableElement(*this)) {
-    LocalFrame* frame = document().frame();
     if (!frame)
       return;
 
@@ -2706,8 +2707,13 @@ void Element::updateFocusAppearance(
         FrameSelection::CloseTyping | FrameSelection::ClearTypingStyle |
             FrameSelection::DoNotSetFocus);
     frame->selection().revealSelection();
-  } else if (layoutObject() && !layoutObject()->isLayoutPart()) {
-    layoutObject()->scrollRectToVisible(boundingBox());
+  } else {
+    // This element is non editable.
+    if (frame)
+      frame->selection().clear();

[yosin_UTC9, 2017/02/09 13:02:17]

Focus and selection are individual identity. We don't want to clear focus here.
Think about caret browsing is an example although chrome doesn't support caret
browsing anymore.

[hugoh_UTC2, 2017/02/11 03:42:22]

True, here we would clear() too often. Let's put this logic in
advanceFocusInDocumentOrder() instead? When tabbing from <input> to <button> the
selected text of <input> should be cleared. Otherwise, we change the current
behavior of tab/shift+tab.

+
+    if (layoutObject() && !layoutObject()->isLayoutPart())
+      layoutObject()->scrollRectToVisible(boundingBox());
   }
 }