Incorporate ComputedStyle::hasTransform when diffing transform styles.

third_party/WebKit/Source/core/paint/PaintLayer.cpp

Index: third_party/WebKit/Source/core/paint/PaintLayer.cpp
diff --git a/third_party/WebKit/Source/core/paint/PaintLayer.cpp b/third_party/WebKit/Source/core/paint/PaintLayer.cpp
index b4c6969b84aa3dba8e4cd623c63b7442f38bf391..6dc32221664c0687234f3b9aedcaae6e58e41b93 100644
--- a/third_party/WebKit/Source/core/paint/PaintLayer.cpp
+++ b/third_party/WebKit/Source/core/paint/PaintLayer.cpp
@@ -389,8 +389,13 @@ void PaintLayer::updateTransformationMatrix() {
 
 void PaintLayer::updateTransform(const ComputedStyle* oldStyle,
                                  const ComputedStyle& newStyle) {
-  if (oldStyle && newStyle.transformDataEquivalent(*oldStyle))
+  // It's possible for the old and new style transform data to be equivalent
+  // while hasTransform() differs, as it checks a number of conditions aside
+  // from just the matrix, including but not limited to animation state.
+  if (oldStyle && oldStyle->hasTransform() == newStyle.hasTransform() &&
+      newStyle.transformDataEquivalent(*oldStyle)) {
     return;
+  }
 
   // hasTransform() on the layoutObject is also true when there is
   // transform-style: preserve-3d or perspective set, so check style too.