Avoid calling isFocusable() during updateLayout.

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

Index: third_party/WebKit/Source/core/dom/Document.cpp
diff --git a/third_party/WebKit/Source/core/dom/Document.cpp b/third_party/WebKit/Source/core/dom/Document.cpp
index aba34c010cce40e02c43c75f28d7b7a799a3c027..bb0c8e5d62330d725e1c9eb5500c898d7c221451 100644
--- a/third_party/WebKit/Source/core/dom/Document.cpp
+++ b/third_party/WebKit/Source/core/dom/Document.cpp
@@ -1731,7 +1731,7 @@ void Document::updateStyleAndLayoutTree()
     if (hoverNode() && !hoverNode()->layoutObject() && frame())
         frame()->eventHandler().dispatchFakeMouseMoveEventSoon();
 
-    if (m_focusedElement && !m_focusedElement->isFocusable())

[tkent, 2016/07/21 00:38:50]

At this line, we already updated style and layout tree, didn't we?
Why we hit the DCHECK failure in isFocusable()?

[kochi, 2016/07/21 01:32:49]

Hmm, yes.
Yesterday I saw another case that needsUpdateLayout flag is not cleared
after layout : https://bugs.chromium.org/p/chromium/issues/detail?id=605746
Maybe some other layout parts introduced a bug recently.

+    if (m_focusedElement)

[esprehn, 2016/07/23 08:37:25]

Note that we can't land this change anyway, since clearFocusedElementSoon()
posts a task. This change would have made all calls to
updateStyleAndLayoutTree() post an unconditional additional task.

not lgtm

         clearFocusedElementSoon();
     layoutViewItem().clearHitTestCache();