Stop explicit inheritance if LayoutStyle doesn't change.

Source/core/layout/style/LayoutStyle.cpp

Index: Source/core/layout/style/LayoutStyle.cpp
diff --git a/Source/core/layout/style/LayoutStyle.cpp b/Source/core/layout/style/LayoutStyle.cpp
index 3915a94c7683873de695056165c52574f38d721e..ac558d30afd62db3b0d6b8bae062d5f16c219cbd 100644
--- a/Source/core/layout/style/LayoutStyle.cpp
+++ b/Source/core/layout/style/LayoutStyle.cpp
@@ -188,14 +188,15 @@ StyleRecalcChange LayoutStyle::stylePropagationDiff(const LayoutStyle* oldStyle,
         || oldStyle->alignItems() != newStyle->alignItems())
         return Reattach;
 
-    if (oldStyle->inheritedNotEqual(*newStyle)
-        || oldStyle->hasExplicitlyInheritedProperties()
-        || newStyle->hasExplicitlyInheritedProperties())
+    if (oldStyle->inheritedNotEqual(*newStyle))
         return Inherit;
 
     if (*oldStyle == *newStyle)
         return diffPseudoStyles(*oldStyle, *newStyle);
 
+    if (oldStyle->hasExplicitlyInheritedProperties())
+        return Inherit;
+
     return NoInherit;
 }
 
@@ -251,7 +252,6 @@ void LayoutStyle::copyNonInheritedFrom(const LayoutStyle& other)
     noninherited_flags.pageBreakBefore = other.noninherited_flags.pageBreakBefore;
     noninherited_flags.pageBreakAfter = other.noninherited_flags.pageBreakAfter;
     noninherited_flags.pageBreakInside = other.noninherited_flags.pageBreakInside;
-    noninherited_flags.explicitInheritance = other.noninherited_flags.explicitInheritance;

[esprehn, 2015/02/13 02:29:13]

Why is it okay not to copy this bit? This seems to break the contract of what
copyNonInheritedFrom does?

     noninherited_flags.hasViewportUnits = other.noninherited_flags.hasViewportUnits;
     if (m_svgStyle != other.m_svgStyle)
         m_svgStyle.access()->copyNonInheritedFrom(other.m_svgStyle.get());