Set a direct compositing reason for 3D transform paint property tree nodes.

As part of this, starts allocating a transform node to represent direct
compositing of will-change:transform elements and their stacking children.

BUG=668342
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2

Review-Url: https://codereview.chromium.org/2571043002
Cr-Commit-Position: refs/heads/master@{#438771}

third_party/WebKit/LayoutTests/FlagExpectations/enable-slimming-paint-v2

@@ -79,6 +79,7 @@ Bug(none) xmlviewer/ [ Skip ]
 Bug(none) broadcastchannel/blobs.html [ Pass Failure ]
 Bug(none) compositing/3d-cube.html [ Failure ]
 Bug(none) compositing/absolute-inside-out-of-view-fixed.html [ Failure ]
+crbug.com/668342 compositing/always-composite-fixed-position-when-descendants-composite.html [ Failure ]
 Bug(none) compositing/animation/hidden-composited.html [ Failure ]
 Bug(none) compositing/backface-visibility/backface-visibility-image.html [ Failure ]
 Bug(none) compositing/backface-visibility/backface-visibility-webgl.html [ Failure ]

third_party/WebKit/Source/core/layout/compositing/CompositingReasonFinder.cpp

@@ -74,7 +74,7 @@ CompositingReasonFinder::potentialCompositingReasonsFromStyle(
 
   const ComputedStyle& style = layoutObject->styleRef();
 
-  if (requiresCompositingForTransform(layoutObject))
+  if (requiresCompositingForTransform(*layoutObject))
     reasons |= CompositingReason3DTransform;
 
   if (style.backfaceVisibility() == BackfaceVisibilityHidden)
@@ -132,12 +132,12 @@ CompositingReasonFinder::potentialCompositingReasonsFromStyle(
 }
 
 bool CompositingReasonFinder::requiresCompositingForTransform(
-    LayoutObject* layoutObject) const {
+    const LayoutObject& layoutObject) {
   // Note that we ask the layoutObject if it has a transform, because the style
   // may have transforms, but the layoutObject may be an inline that doesn't
   // support them.
-  return layoutObject->hasTransformRelatedProperty() &&
-         layoutObject->style()->has3DTransform();
+  return layoutObject.hasTransformRelatedProperty() &&
+         layoutObject.styleRef().has3DTransform();
 }
 
 CompositingReasons CompositingReasonFinder::nonStyleDeterminedDirectReasons(
@@ -171,7 +171,7 @@ CompositingReasons CompositingReasonFinder::nonStyleDeterminedDirectReasons(
 }
 
 bool CompositingReasonFinder::requiresCompositingForAnimation(
-    const ComputedStyle& style) const {
+    const ComputedStyle& style) {
   if (style.subtreeWillChangeContents())
     return style.isRunningAnimationOnCompositor();
 

third_party/WebKit/Source/core/layout/compositing/CompositingReasonFinder.h

@@ -31,14 +31,13 @@ class CompositingReasonFinder {
 
   bool hasOverflowScrollTrigger() const;
   bool requiresCompositingForScrollableFrame() const;
-  bool requiresCompositingForAnimation(const ComputedStyle&) const;
+  static bool requiresCompositingForAnimation(const ComputedStyle&);
+  static bool requiresCompositingForTransform(const LayoutObject&);
 
  private:
   bool isMainFrame() const;
 
   CompositingReasons nonStyleDeterminedDirectReasons(const PaintLayer*) const;
-
-  bool requiresCompositingForTransform(LayoutObject*) const;
   bool requiresCompositingForScrollDependentPosition(const PaintLayer*) const;
 
   LayoutView& m_layoutView;

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

@@ -9,6 +9,7 @@
 #include "core/frame/Settings.h"
 #include "core/layout/LayoutInline.h"
 #include "core/layout/LayoutView.h"
+#include "core/layout/compositing/CompositingReasonFinder.h"
 #include "core/layout/svg/LayoutSVGRoot.h"
 #include "core/paint/FindPropertiesNeedingUpdate.h"
 #include "core/paint/ObjectPaintProperties.h"
@@ -312,6 +313,19 @@ void PaintPropertyTreeBuilder::updateTransformForNonRootSVG(
   }
 }
 
+static CompositingReasons compositingReasonsForTransform(
+    const LayoutObject& object) {
+  CompositingReasons compositingReasons = CompositingReasonNone;
+  if (CompositingReasonFinder::requiresCompositingForTransform(object))
+    compositingReasons |= CompositingReason3DTransform;
+
+  if (object.styleRef().hasWillChangeCompositingHint() &&
+      !object.styleRef().subtreeWillChangeContents())
+    compositingReasons |= CompositingReasonWillChangeCompositingHint;
+
+  return compositingReasons;
+}
+
 void PaintPropertyTreeBuilder::updateTransform(
     const LayoutObject& object,
     PaintPropertyTreeBuilderContext& context) {
@@ -322,7 +336,16 @@ void PaintPropertyTreeBuilder::updateTransform(
 
   if (object.needsPaintPropertyUpdate() || context.forceSubtreeUpdate) {
     const ComputedStyle& style = object.styleRef();
-    if (object.isBox() && (style.hasTransform() || style.preserves3D())) {
+
+    CompositingReasons compositingReasons =
+        compositingReasonsForTransform(object);
+
+    // A transform node is allocated for transforms, preserves-3d and any
+    // direct compositing reason. The latter is required because this is the
+    // only way to represent compositing both an element and its stacking
+    // descendants.
+    if (object.isBox() && (style.hasTransform() || style.preserves3D() ||
+                           compositingReasons != CompositingReasonNone)) {
       TransformationMatrix matrix;
       style.applyTransform(
           matrix, toLayoutBox(object).size(),
@@ -342,7 +365,8 @@ void PaintPropertyTreeBuilder::updateTransform(
       context.forceSubtreeUpdate |= properties.updateTransform(
           context.current.transform, matrix,
           transformOrigin(toLayoutBox(object)),
-          context.current.shouldFlattenInheritedTransform, renderingContextID);
+          context.current.shouldFlattenInheritedTransform, renderingContextID,
+          compositingReasons);
     } else {
       if (auto* properties = object.getMutableForPainting().paintProperties())
         context.forceSubtreeUpdate |= properties->clearTransform();

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

@@ -334,7 +334,12 @@ TEST_P(PaintPropertyTreeBuilderTest, Perspective) {
 }
 
 TEST_P(PaintPropertyTreeBuilderTest, Transform) {
-  loadTestData("transform.html");
+  setBodyInnerHTML(
+      "<style> body { margin: 0 } </style>"
+      "<div id='transform' style='margin-left: 50px; margin-top: 100px;"
+      "    width: 400px; height: 300px;"
+      "    transform: translate3D(123px, 456px, 789px)'>"
+      "</div>");
 
   Element* transform = document().getElementById("transform");
   const ObjectPaintProperties* transformProperties =
@@ -349,9 +354,86 @@ TEST_P(PaintPropertyTreeBuilderTest, Transform) {
             transformProperties->paintOffsetTranslation()->matrix());
   EXPECT_EQ(frameScrollTranslation(),
             transformProperties->paintOffsetTranslation()->parent());
+
+  EXPECT_TRUE(transformProperties->transform()->hasDirectCompositingReasons());
+  EXPECT_FALSE(frameScrollTranslation()->hasDirectCompositingReasons());
+
   CHECK_EXACT_VISUAL_RECT(LayoutRect(173, 556, 400, 300),
                           transform->layoutObject(),
                           document().view()->layoutView());
+
+  transform->setAttribute(
+      HTMLNames::styleAttr,
+      "margin-left: 50px; margin-top: 100px; width: 400px; height: 300px;");
+  document().view()->updateAllLifecyclePhases();
+  EXPECT_EQ(nullptr, transform->layoutObject()->paintProperties()->transform());
+
+  transform->setAttribute(
+      HTMLNames::styleAttr,
+      "margin-left: 50px; margin-top: 100px; width: 400px; height: 300px; "
+      "transform: translate3D(123px, 456px, 789px)");
+  document().view()->updateAllLifecyclePhases();
+  EXPECT_EQ(
+      TransformationMatrix().translate3d(123, 456, 789),
+      transform->layoutObject()->paintProperties()->transform()->matrix());
+}
+
+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 =
+      transform->layoutObject()->paintProperties();
+
+  EXPECT_EQ(TransformationMatrix(), transformProperties->transform()->matrix());
+  EXPECT_EQ(FloatPoint3D(200, 150, 0),
+            transformProperties->transform()->origin());
+  EXPECT_EQ(nullptr, transformProperties->paintOffsetTranslation());
+  EXPECT_TRUE(transformProperties->transform()->hasDirectCompositingReasons());
+
+  CHECK_EXACT_VISUAL_RECT(LayoutRect(50, 100, 400, 300),
+                          transform->layoutObject(),
+                          document().view()->layoutView());
+
+  transform->setAttribute(
+      HTMLNames::styleAttr,
+      "margin-left: 50px; margin-top: 100px; width: 400px; height: 300px;");
+  document().view()->updateAllLifecyclePhases();
+  EXPECT_EQ(nullptr, transform->layoutObject()->paintProperties()->transform());
+
+  transform->setAttribute(
+      HTMLNames::styleAttr,
+      "margin-left: 50px; margin-top: 100px; width: 400px; height: 300px; "
+      "will-change: transform");
+  document().view()->updateAllLifecyclePhases();
+  EXPECT_EQ(
+      TransformationMatrix(),
+      transform->layoutObject()->paintProperties()->transform()->matrix());
+}
+
+TEST_P(PaintPropertyTreeBuilderTest, WillChangeContents) {
+  setBodyInnerHTML(
+      "<style> body { margin: 0 } </style>"
+      "<div id='transform' style='margin-left: 50px; margin-top: 100px;"
+      "    width: 400px; height: 300px;"
+      "    will-change: transform, contents'>"
+      "</div>");
+
+  Element* transform = document().getElementById("transform");
+  const ObjectPaintProperties* transformProperties =
+      transform->layoutObject()->paintProperties();
+
+  EXPECT_EQ(nullptr, transformProperties->transform());
+  EXPECT_EQ(nullptr, transformProperties->paintOffsetTranslation());
+
+  CHECK_EXACT_VISUAL_RECT(LayoutRect(50, 100, 400, 300),
+                          transform->layoutObject(),
+                          document().view()->layoutView());
 }
 
 TEST_P(PaintPropertyTreeBuilderTest, RelativePositionInline) {

third_party/WebKit/Source/core/paint/test_data/transform.html

-<style>
-body {
-    margin: 0;
-}
-
-#transform {
-    margin-left: 50px;
-    margin-top: 100px;
-
-    width: 400px;
-    height: 300px;
-
-    transform: translate3D(123px, 456px, 789px);
-}
-</style>
-<div id="transform">
-</div>

third_party/WebKit/Source/platform/graphics/paint/TransformPaintPropertyNode.h

@@ -7,6 +7,7 @@
 
 #include "platform/PlatformExport.h"
 #include "platform/geometry/FloatPoint3D.h"
+#include "platform/graphics/CompositingReasons.h"
 #include "platform/transforms/TransformationMatrix.h"
 #include "wtf/PassRefPtr.h"
 #include "wtf/RefCounted.h"
@@ -32,17 +33,20 @@ class PLATFORM_EXPORT TransformPaintPropertyNode
       const TransformationMatrix& matrix,
       const FloatPoint3D& origin,
       bool flattensInheritedTransform = false,
-      unsigned renderingContextID = 0) {
+      unsigned renderingContextID = 0,
+      CompositingReasons directCompositingReasons = CompositingReasonNone) {
     return adoptRef(new TransformPaintPropertyNode(
         matrix, origin, std::move(parent), flattensInheritedTransform,
-        renderingContextID));
+        renderingContextID, directCompositingReasons));
   }
 
-  void update(PassRefPtr<const TransformPaintPropertyNode> parent,
-              const TransformationMatrix& matrix,
-              const FloatPoint3D& origin,
-              bool flattensInheritedTransform = false,
-              unsigned renderingContextID = 0) {
+  void update(
+      PassRefPtr<const TransformPaintPropertyNode> parent,
+      const TransformationMatrix& matrix,
+      const FloatPoint3D& origin,
+      bool flattensInheritedTransform = false,
+      unsigned renderingContextID = 0,
+      CompositingReasons directCompositingReasons = CompositingReasonNone) {
     DCHECK(!isRoot());
     DCHECK(parent != this);
     m_parent = parent;
@@ -50,6 +54,7 @@ class PLATFORM_EXPORT TransformPaintPropertyNode
     m_origin = origin;
     m_flattensInheritedTransform = flattensInheritedTransform;
     m_renderingContextID = renderingContextID;
+    m_directCompositingReasons = directCompositingReasons;
   }
 
   const TransformationMatrix& matrix() const { return m_matrix; }
@@ -67,6 +72,10 @@ class PLATFORM_EXPORT TransformPaintPropertyNode
     return m_flattensInheritedTransform;
   }
 
+  bool hasDirectCompositingReasons() const {
+    return m_directCompositingReasons != CompositingReasonNone;
+  }
+
   // Content whose transform nodes have a common rendering context ID are 3D
   // sorted. If this is 0, content will not be 3D sorted.
   unsigned renderingContextID() const { return m_renderingContextID; }
@@ -76,9 +85,9 @@ class PLATFORM_EXPORT TransformPaintPropertyNode
   // The clone function is used by FindPropertiesNeedingUpdate.h for recording
   // a transform node before it has been updated, to later detect changes.
   PassRefPtr<TransformPaintPropertyNode> clone() const {
-    return adoptRef(new TransformPaintPropertyNode(m_matrix, m_origin, m_parent,
-                                                   m_flattensInheritedTransform,
-                                                   m_renderingContextID));
+    return adoptRef(new TransformPaintPropertyNode(
+        m_matrix, m_origin, m_parent, m_flattensInheritedTransform,
+        m_renderingContextID, m_directCompositingReasons));
   }
 
   // The equality operator is used by FindPropertiesNeedingUpdate.h for checking
@@ -99,18 +108,21 @@ class PLATFORM_EXPORT TransformPaintPropertyNode
       const FloatPoint3D& origin,
       PassRefPtr<const TransformPaintPropertyNode> parent,
       bool flattensInheritedTransform,
-      unsigned renderingContextID)
+      unsigned renderingContextID,
+      CompositingReasons directCompositingReasons)
       : m_matrix(matrix),
         m_origin(origin),
         m_parent(parent),
         m_flattensInheritedTransform(flattensInheritedTransform),
-        m_renderingContextID(renderingContextID) {}
+        m_renderingContextID(renderingContextID),
+        m_directCompositingReasons(directCompositingReasons) {}
 
   TransformationMatrix m_matrix;
   FloatPoint3D m_origin;
   RefPtr<const TransformPaintPropertyNode> m_parent;
   bool m_flattensInheritedTransform;
   unsigned m_renderingContextID;
+  CompositingReasons m_directCompositingReasons;
 };
 
 // Redeclared here to avoid ODR issues.