Do not use LayoutProgress for a UA shadow element of a PROGRESS element.

third_party/WebKit/Source/core/layout/LayoutProgress.cpp

Index: third_party/WebKit/Source/core/layout/LayoutProgress.cpp
diff --git a/third_party/WebKit/Source/core/layout/LayoutProgress.cpp b/third_party/WebKit/Source/core/layout/LayoutProgress.cpp
index 9ec5d1bfa1ec38637c52c3963cb7a2c68be6927e..d5367f6c2645f72169c07da2f2e4caf3202c9184 100644
--- a/third_party/WebKit/Source/core/layout/LayoutProgress.cpp
+++ b/third_party/WebKit/Source/core/layout/LayoutProgress.cpp
@@ -27,7 +27,7 @@
 
 namespace blink {
 
-LayoutProgress::LayoutProgress(HTMLElement* element)
+LayoutProgress::LayoutProgress(HTMLProgressElement* element)
     : LayoutBlockFlow(element)
     , m_position(HTMLProgressElement::InvalidPosition)
     , m_animationStartTime(0)
@@ -111,14 +111,7 @@ void LayoutProgress::updateAnimationState()
 
 HTMLProgressElement* LayoutProgress::progressElement() const
 {
-    if (!node())
-        return nullptr;
-
-    if (isHTMLProgressElement(*node()))
-        return toHTMLProgressElement(node());
-
-    ASSERT(node()->shadowHost());
-    return toHTMLProgressElement(node()->shadowHost());
+    return toHTMLProgressElement(node());
 }
 
 } // namespace blink