Constrain transform animation direct compositing reason to transforms.

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

Index: third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilderTest.cpp
diff --git a/third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilderTest.cpp b/third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilderTest.cpp
index 92e368d822a3aecb58d75cff1fe8bebb5b3c0b69..1a5246a571729a035d5309aa0265981fd1790295 100644
--- a/third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilderTest.cpp
+++ b/third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilderTest.cpp
@@ -403,6 +403,30 @@ TEST_P(PaintPropertyTreeBuilderTest,
   EXPECT_TRUE(transformProperties->transform()->hasDirectCompositingReasons());
 }
 
+TEST_P(PaintPropertyTreeBuilderTest,
+       OpacityAnimationDoesNotCreateTransformNode) {
+  setBodyInnerHTML(
+      "<style>"
+      "div {"
+      "  width: 100px;"
+      "  height: 100px;"
+      "  background-color: red;"
+      "  animation-name: example;"
+      "  animation-duration: 4s;"
+      "}"
+      "@keyframes example {"
+      "  from { opacity: 0.0;}"
+      "  to { opacity: 1.0;}"
+      "}"
+      "</style>"
+      "<div id='target'></div>");
+
+  Element* target = document().getElementById("target");

[pdr., 2016/12/21 00:02:24]

Can you add a test to PaintPropertyTreeUpdateTests.cpp where we remove the
animation and ensure the transform is removed?

[wkorman, 2016/12/21 18:58:49]

Done.

+  const ObjectPaintProperties* properties =
+      target->layoutObject()->paintProperties();
+  EXPECT_EQ(nullptr, properties->transform());
+}
+
 TEST_P(PaintPropertyTreeBuilderTest, WillChangeTransform) {
   setBodyInnerHTML(
       "<style> body { margin: 0 } </style>"