Constrain transform animation direct compositing reason to transforms.

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

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/paint/PaintPropertyTreeBuilderTest.h"
 
 #include "core/html/HTMLIFrameElement.h"
 #include "core/layout/LayoutTreeAsText.h"
 #include "core/paint/ObjectPaintProperties.h"
 #include "core/paint/PaintPropertyTreePrinter.h"
@@ skipping 385 matching lines @@
       "<div id='transform' "
       "    style='animation-name: test; animation-duration: 1s'>"
       "</div>");
 
   Element* transform = document().getElementById("transform");
   const ObjectPaintProperties* transformProperties =
       transform->layoutObject()->paintProperties();
   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>"
       "<div id='transform' style='margin-left: 50px; margin-top: 100px;"
       "    width: 400px; height: 300px;"
       "    will-change: transform'>"
       "</div>");
 
   Element* transform = document().getElementById("transform");
   const ObjectPaintProperties* transformProperties =
@@ skipping 2428 matching lines @@
   EXPECT_EQ(framePreTranslation(),
             childProperties->paintOffsetTranslation()->parent());
   EXPECT_EQ(childProperties->paintOffsetTranslation(),
             childPaintState.transform());
   // This will change once we added clip expansion node.
   EXPECT_EQ(filterProperties->effect()->outputClip(), childPaintState.clip());
   EXPECT_EQ(filterProperties->effect(), childPaintState.effect());
 }
 
 }  // namespace blink