Allow an element in shadow tree in <dialog> to be initially focused.

third_party/WebKit/Source/core/html/HTMLDialogElement.cpp

Index: third_party/WebKit/Source/core/html/HTMLDialogElement.cpp
diff --git a/third_party/WebKit/Source/core/html/HTMLDialogElement.cpp b/third_party/WebKit/Source/core/html/HTMLDialogElement.cpp
index 9edc5883e4ea38e02f6a61618fe0434fdac93113..39ed61e731d906bb083d42dbcd7e6e6bc98b0fd6 100644
--- a/third_party/WebKit/Source/core/html/HTMLDialogElement.cpp
+++ b/third_party/WebKit/Source/core/html/HTMLDialogElement.cpp
@@ -28,7 +28,7 @@
 #include "bindings/core/v8/ExceptionState.h"
 #include "core/dom/AXObjectCache.h"
 #include "core/dom/ExceptionCode.h"
-#include "core/dom/NodeTraversal.h"
+#include "core/dom/shadow/FlatTreeTraversal.h"
 #include "core/events/Event.h"
 #include "core/frame/FrameView.h"
 #include "core/frame/UseCounter.h"
@@ -42,13 +42,16 @@ using namespace HTMLNames;
 // This function chooses the focused element when show() or showModal() is
 // invoked, as described in their spec.
 static void setFocusForDialog(HTMLDialogElement* dialog) {
-  Element* focusableDescendant = 0;
-  Node* next = 0;
-  for (Node* node = dialog->firstChild(); node; node = next) {
-    if (isHTMLDialogElement(*node))
-      next = NodeTraversal::nextSkippingChildren(*node, dialog);
-    else
-      next = NodeTraversal::next(*node, dialog);
+  Element* focusableDescendant = nullptr;
+  Node* next = nullptr;
+
+  // TODO(kochi): Use FlatTreeTraversal for finding focusable element in Shadow

[Dan Beam, 2017/02/27 04:16:25]

i think this is kinda of confusing, because it seems like (from reading this
comment) that the code needs to be updated to use FlatTreeTraversal (but it
already is).  maybe something like:

// Whether to use shadow DOM or not is currently unspecified. This may change at
// any time. See crbug.com/383230 and https://github.com/whatwg/html/issue/2393.

[kochi, 2017/02/28 06:10:28]

Thanks for the feedback, updated the comment.

+  // DOM, which is not yet specified. See crbug/383230 and
+  // https://github.com/whatwg/html/issue/2393 .
+  for (Node* node = FlatTreeTraversal::firstChild(*dialog); node; node = next) {

[hayato, 2017/02/28 06:12:36]

Distribution is not dirty here? If it is dirty, it would hit the assertion.

+    next = isHTMLDialogElement(*node)
+               ? FlatTreeTraversal::nextSkippingChildren(*node, dialog)
+               : FlatTreeTraversal::next(*node, dialog);
 
     if (!node->isElementNode())
       continue;