Have Element::ensureMutableInlineStyle() return a reference

Source/core/css/resolver/StyleResolver.cpp

Index: Source/core/css/resolver/StyleResolver.cpp
diff --git a/Source/core/css/resolver/StyleResolver.cpp b/Source/core/css/resolver/StyleResolver.cpp
index 7b4c743ab6f68652e704cd0cb597246e7608daa0..53348df162a2e4dbeb211c5f3735659ab860ba47 100644
--- a/Source/core/css/resolver/StyleResolver.cpp
+++ b/Source/core/css/resolver/StyleResolver.cpp
@@ -741,8 +741,7 @@ PassRefPtr<RenderStyle> StyleResolver::styleForKeyframe(Element* element, const
     StyleResolverState state(document(), element, parentStyle);
 
     MatchResult result;
-    if (keyframe->properties())
-        result.addMatchedProperties(keyframe->properties());
+    result.addMatchedProperties(&keyframe->properties());
 
     ASSERT(!state.style());
 
@@ -767,10 +766,8 @@ PassRefPtr<RenderStyle> StyleResolver::styleForKeyframe(Element* element, const
     // We don't need to bother with !important. Since there is only ever one
     // decl, there's nothing to override. So just add the first properties.
     bool inheritedOnly = false;
-    if (keyframe->properties()) {
-        applyMatchedProperties<AnimationProperties>(state, result, false, 0, result.matchedProperties.size() - 1, inheritedOnly);
-        applyMatchedProperties<HighPriorityProperties>(state, result, false, 0, result.matchedProperties.size() - 1, inheritedOnly);
-    }
+    applyMatchedProperties<AnimationProperties>(state, result, false, 0, result.matchedProperties.size() - 1, inheritedOnly);
+    applyMatchedProperties<HighPriorityProperties>(state, result, false, 0, result.matchedProperties.size() - 1, inheritedOnly);
 
     // If our font got dirtied, go ahead and update it now.
     updateFont(state);
@@ -780,8 +777,7 @@ PassRefPtr<RenderStyle> StyleResolver::styleForKeyframe(Element* element, const
         StyleBuilder::applyProperty(CSSPropertyLineHeight, state, state.lineHeightValue());
 
     // Now do rest of the properties.
-    if (keyframe->properties())
-        applyMatchedProperties<LowPriorityProperties>(state, result, false, 0, result.matchedProperties.size() - 1, inheritedOnly);
+    applyMatchedProperties<LowPriorityProperties>(state, result, false, 0, result.matchedProperties.size() - 1, inheritedOnly);
 
     // If our font got dirtied by one of the non-essential font props,
     // go ahead and update it a second time.