Clear mutable inline style when it is empty.

Source/core/dom/Element.cpp

Index: Source/core/dom/Element.cpp
diff --git a/Source/core/dom/Element.cpp b/Source/core/dom/Element.cpp
index ced2bd06440792fe0a24dbe5deac5b25b4f45e55..a4d2253ef8f179410d823cbbf79026283e95bf46 100644
--- a/Source/core/dom/Element.cpp
+++ b/Source/core/dom/Element.cpp
@@ -3432,8 +3432,9 @@ void Element::synchronizeStyleAttributeInternal() const
     ASSERT(elementData());
     ASSERT(elementData()->m_styleAttributeIsDirty);
     elementData()->m_styleAttributeIsDirty = false;
-    if (const StylePropertySet* inlineStyle = this->inlineStyle())
-        const_cast<Element*>(this)->setSynchronizedLazyAttribute(styleAttr, inlineStyle->asText());
+    const StylePropertySet* inlineStyle = this->inlineStyle();
+    const_cast<Element*>(this)->setSynchronizedLazyAttribute(styleAttr,
+        inlineStyle ? AtomicString(inlineStyle->asText()) : nullAtom);
 }
 
 CSSStyleDeclaration* Element::style()
@@ -3456,6 +3457,13 @@ MutableStylePropertySet* Element::ensureMutableInlineStyle()
     return toMutableStylePropertySet(inlineStyle);
 }
 
+void Element::clearMutableInlineStyleIfEmpty()
+{
+    if (ensureMutableInlineStyle()->isEmpty()) {
+        ensureUniqueElementData()->m_inlineStyle.clear();
+    }
+}
+
 PropertySetCSSStyleDeclaration* Element::inlineStyleCSSOMWrapper()
 {
     if (!inlineStyle() || !inlineStyle()->hasCSSOMWrapper())
@@ -3564,7 +3572,7 @@ bool Element::removeInlineStyleProperty(CSSPropertyID propertyID)
 void Element::removeAllInlineStyleProperties()
 {
     ASSERT(isStyledElement());
-    if (!inlineStyle() || inlineStyle()->isEmpty())
+    if (!inlineStyle())
         return;
     ensureMutableInlineStyle()->clear();
     inlineStyleChanged();