MacViews: Emit NOTIMPLEMENTED() in NativeWidgetMac::ViewRemoved() only when potentially dragging

ui/views/widget/native_widget_mac.mm

Index: ui/views/widget/native_widget_mac.mm
diff --git a/ui/views/widget/native_widget_mac.mm b/ui/views/widget/native_widget_mac.mm
index a9af6fe6d67fb2e632b905e14619ccc86540617f..04adf3012019ab467cb14515ffb005afa6fc76a1 100644
--- a/ui/views/widget/native_widget_mac.mm
+++ b/ui/views/widget/native_widget_mac.mm
@@ -194,7 +194,11 @@ void NativeWidgetMac::ReorderNativeViews() {
 }
 
 void NativeWidgetMac::ViewRemoved(View* view) {
-  NOTIMPLEMENTED();
+  // TODO(tapted): Something for drag and drop might be needed here in future.
+  // See http://crbug.com/464581. A NOTIMPLEMENTED() here makes a lot of spam,
+  // so only emit it when a drag and drop could be likely.
+  if (IsMouseButtonDown())
+    NOTIMPLEMENTED();
 }
 
 void NativeWidgetMac::SetNativeWindowProperty(const char* name, void* value) {