Constrain transform animation direct compositing reason to transforms.

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

Index: third_party/WebKit/Source/core/paint/PaintPropertyTreeUpdateTests.cpp
diff --git a/third_party/WebKit/Source/core/paint/PaintPropertyTreeUpdateTests.cpp b/third_party/WebKit/Source/core/paint/PaintPropertyTreeUpdateTests.cpp
index e983490c89dc7f94ba7b167c155eb4c6399d4b10..ba68026e7d176fafac752a41b441f7e4ec28877e 100644
--- a/third_party/WebKit/Source/core/paint/PaintPropertyTreeUpdateTests.cpp
+++ b/third_party/WebKit/Source/core/paint/PaintPropertyTreeUpdateTests.cpp
@@ -441,4 +441,29 @@ TEST_P(PaintPropertyTreeUpdateTest,
   EXPECT_EQ(nullptr, frameScroll(childFrameView));
 }
 
+TEST_P(PaintPropertyTreeUpdateTest,
+       TransformNodeWithAnimationLosesNodeWhenAnimationRemoved) {
+  setBodyInnerHTML(
+      "<style>"
+      "@keyframes test {"
+      "  0% { transform: translate(1em, 1em) } "
+      "  100% { transform: translate(2em, 2em) } "
+      "} "
+      ".animate { "
+      "  animation-name: test; "
+      "  animation-duration: 1s "
+      "}"
+      "</style>"
+      "<div id='target' class='animate'></div>");
+  Element* target = document().getElementById("target");
+  const ObjectPaintProperties* properties =
+      target->layoutObject()->paintProperties();
+  EXPECT_TRUE(properties->transform()->hasDirectCompositingReasons());
+
+  // Removing the animation should remove the transform node.
+  target->removeAttribute(HTMLNames::classAttr);
+  document().view()->updateAllLifecyclePhases();
+  EXPECT_EQ(nullptr, properties->transform());
+}
+
 }  // namespace blink