Skip the whole shadow tree when its tabindex is -1.

Source/core/page/FocusController.cpp

Index: Source/core/page/FocusController.cpp
diff --git a/Source/core/page/FocusController.cpp b/Source/core/page/FocusController.cpp
index db3dc8cc5b048b47bc5494a8fb43bec9202693f0..ec016f6a5c0a909e81a6dc5b2e5870853f9a3349 100644
--- a/Source/core/page/FocusController.cpp
+++ b/Source/core/page/FocusController.cpp
@@ -554,24 +554,25 @@ Element* FocusController::findFocusableElementRecursivelyForward(const FocusNavi
     if (!found)
         return nullptr;
     if (isShadowHostDelegatesFocus(*found)) {
-        if (isShadowHostWithoutCustomFocusLogic(*found)) {
+        // If tabindex is positive, find focusable node inside its shadow tree.
+        if (found->tabIndex() >= 0 && isShadowHostWithoutCustomFocusLogic(*found)) {
             FocusNavigationScope innerScope = FocusNavigationScope::ownedByShadowHost(*found);
-            Element* foundInInnerFocusScope = findFocusableElementRecursivelyForward(innerScope, nullptr);
-            return foundInInnerFocusScope ? foundInInnerFocusScope : findFocusableElementRecursivelyForward(scope, found);
+            if (Element* foundInInnerFocusScope = findFocusableElementRecursivelyForward(innerScope, nullptr))
+                return foundInInnerFocusScope;
         }
-        // Skip to the next node.
-        if (!isNonFocusableFocusScopeOwner(*found))

[kochi, 2015/06/17 07:11:49]

In the previous CL[1], I added this line (563) but this code was wrong.

Lines 557-564 are executed when |found| is a shadow host and its
|delegatesFocus|
is true.  It also implies |found| is not a UA shadow root (as no one uses
|delegatesFocus| so far), thus on line 557 isShadowHostWithoutCustomFocusLogic()
returned always true, and lines 563-564 were never executed.

[1]:
https://codereview.chromium.org/1174893002/diff/40001/Source/core/page/FocusC...

-            found = findFocusableElementRecursivelyForward(scope, found);
+        // Skip to the next node in the same scope.
+        found = findFocusableElementRecursivelyForward(scope, found);
     }
     if (!found || !isNonFocusableFocusScopeOwner(*found))
         return found;
 
-    // Now |found| is on a focusable scope owner (either shadow host or <shadow>)
+    // Now |found| is on a non focusable scope owner (either shadow host or <shadow>)

[kochi, 2015/06/17 07:11:49]

The comment was wrong ;(

     // Find inside the inward scope and return it if found. Otherwise continue searching in the same
     // scope.
     FocusNavigationScope innerScope = FocusNavigationScope::ownedByNonFocusableFocusScopeOwner(*found);
-    Element* foundInInnerFocusScope = findFocusableElementRecursivelyForward(innerScope, nullptr);
-    return foundInInnerFocusScope ? foundInInnerFocusScope : findFocusableElementRecursivelyForward(scope, found);
+    if (Element* foundInInnerFocusScope = findFocusableElementRecursivelyForward(innerScope, nullptr))
+        return foundInInnerFocusScope;
+    return findFocusableElementRecursivelyForward(scope, found);

[kochi, 2015/06/17 07:11:50]

This chunk does not change the logic, but aligned style with lines 559-561.
It can be extracted to a function, but this is small and I keep them.

 }
 
 Element* FocusController::findFocusableElementRecursivelyBackward(const FocusNavigationScope& scope, Node* start)
@@ -594,6 +595,11 @@ Element* FocusController::findFocusableElementRecursivelyBackward(const FocusNav
         return found;
     }
 
+    // If delegatesFocus is true and tabindex is negative, skip the whole shadow tree under the
+    // shadow host.
+    if (isShadowHostDelegatesFocus(*found) && found->tabIndex() < 0)
+        return findFocusableElementRecursivelyBackward(scope, found);
+
     // Now |found| is on a non focusable scope owner (either shadow host or <shadow>).
     // Find focusable node in decendant scope. If not found, find next focusable node within the
     // current scope.