Do not send redundant selectionchange-events (decouple focus)

third_party/WebKit/Source/core/page/FocusController.cpp

Index: third_party/WebKit/Source/core/page/FocusController.cpp
diff --git a/third_party/WebKit/Source/core/page/FocusController.cpp b/third_party/WebKit/Source/core/page/FocusController.cpp
index de9da91658722ce16c2e4d1f9ba55da8cf1a3666..47e312dd3b9e9e09804d037d32d9e804b700a874 100644
--- a/third_party/WebKit/Source/core/page/FocusController.cpp
+++ b/third_party/WebKit/Source/core/page/FocusController.cpp
@@ -1076,6 +1076,9 @@ static void clearSelectionIfNeeded(LocalFrame* oldFocusedFrame,
       selectionStartNode->isDescendantOf(newFocusedElement))
     return;
 
+  if (newFocusedElement && newFocusedElement->isTextControl())

[yosin_UTC9, 2017/01/05 05:35:33]

Should we also bail out for content editable?

Rather than adding more condition, I think it is better to get rid of this
function, clearSelecitonIfNeeded()
and ask FrameSelection to clear selection if new focus element can't have
selection.

[hugoh_UTC2, 2017/01/06 17:31:44]

Yes, you're right. When focus jumps from <input> to <p contenteditable> I see
that Blink calls into didChangeSelection twice. I added another condition for
this and a unit test that also checks this. 
You mean clear the selection if the new focused element _can_ have a selection?
Or, does it matter? Don't we always want to clear the selection when focus
moves?

+    return;
+
   if (!enclosingTextControl(selectionStartNode))
     return;