Refactor to centralize code which decides whether ObjectPaintProperties are needed.

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

 // Copyright 2016 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/html/HTMLIFrameElement.h"
 #include "core/paint/PaintPropertyTreeBuilderTest.h"
 #include "core/paint/PaintPropertyTreePrinter.h"
 
 namespace blink {
 
@@ skipping 534 matching lines @@
        TransformNodeWithAnimationLosesNodeWhenAnimationRemoved) {
   LoadTestData("transform-animation.html");
   Element* target = GetDocument().GetElementById("target");
   const ObjectPaintProperties* properties =
       target->GetLayoutObject()->PaintProperties();
   EXPECT_TRUE(properties->Transform()->HasDirectCompositingReasons());
 
   // Removing the animation should remove the transform node.
   target->removeAttribute(HTMLNames::classAttr);
   GetDocument().View()->UpdateAllLifecyclePhases();
-  EXPECT_EQ(nullptr, properties->Transform());
+  EXPECT_EQ(nullptr, target->GetLayoutObject()->PaintProperties());

[pdr., 2017/04/20 22:56:28]

Can you add a comment here so we don't accidentally refactor this away in the
future? Something like:
// Ensure the paint properties object was cleared as it is no longer needed.
(Or add a new test of the paint property clearing optimization)

[chrishtr, 2017/04/21 01:20:02]

Added comment.

 }
 
 TEST_P(PaintPropertyTreeUpdateTest,
        EffectNodeWithAnimationLosesNodeWhenAnimationRemoved) {
   LoadTestData("opacity-animation.html");
   Element* target = GetDocument().GetElementById("target");
   const ObjectPaintProperties* properties =
       target->GetLayoutObject()->PaintProperties();
   EXPECT_TRUE(properties->Effect()->HasDirectCompositingReasons());
 
   // Removing the animation should remove the effect node.
   target->removeAttribute(HTMLNames::classAttr);
   GetDocument().View()->UpdateAllLifecyclePhases();
-  EXPECT_EQ(nullptr, properties->Effect());
+  EXPECT_EQ(nullptr, target->GetLayoutObject()->PaintProperties());
 }
 
 TEST_P(PaintPropertyTreeUpdateTest,
        TransformNodeLosesCompositorElementIdWhenAnimationRemoved) {
   LoadTestData("transform-animation.html");
 
   Element* target = GetDocument().GetElementById("target");
   target->setAttribute(HTMLNames::styleAttr, "transform: translateX(2em)");
   GetDocument().View()->UpdateAllLifecyclePhases();
 
@@ skipping 165 matching lines @@
   EXPECT_TRUE(transform->FlattensInheritedTransform());
 
   GetDocument().GetElementById("parent")->setAttribute(
       HTMLNames::styleAttr, "transform-style: preserve-3d");
   GetDocument().View()->UpdateAllLifecyclePhases();
   EXPECT_EQ(transform, child->PaintProperties()->Transform());
   EXPECT_FALSE(transform->FlattensInheritedTransform());
 }
 
 }  // namespace blink