Reland "Fix TransformNode::IsAffectedByOuterViewportBoundsDelta()"

This reverts commit c7cb1a8e.

Use a more reliable way to check if a fixed-pos element's container
is LayoutView.

The previous method of checking parent transform was not reliable
because the fixed-pos container may not create transform nodes.

Original change's description:
> Revert "Fix TransformNode::IsAffectedByOuterViewportBoundsDelta()"
>
> This reverts commit ea5c2a2c.
>
> Reason for revert: Checking the parent transform to check if a fix-pos
> element is contained by LayoutView is not reliable.
>
> Original change's description:
> > Fix TransformNode::IsAffectedByOuterViewportBoundsDelta()
> >
> > Don't set the flag in the following cases:
> > 1. The fixed element is contained by an ancestor below the LayoutView;
> > 2. The fixed element is not in the main frame.
> >
> > Bug: 978774
> > Change-Id: I430dc968c0d016ac9bee4f4934508703a3b90645
> > Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1680938
> > Reviewed-by: David Bokan <bokan@chromium.org>
> > Reviewed-by: Philip Rogers <pdr@chromium.org>
> > Commit-Queue: Xianzhu Wang <wangxianzhu@chromium.org>
> > Cr-Commit-Position: refs/heads/master@{#673239}
>
> TBR=wangxianzhu@chromium.org,bokan@chromium.org,pdr@chromium.org
>
> Change-Id: I120ced5c25468a81e0d9ec227073597dce7bb2c8
> No-Presubmit: true
> No-Tree-Checks: true
> No-Try: true
> Bug: 978774
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1680734
> Reviewed-by: Xianzhu Wang <wangxianzhu@chromium.org>
> Commit-Queue: Xianzhu Wang <wangxianzhu@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#673370}

Change-Id: I5fc8f9c354f616068899b967160425d481dc2c26
Bug: 978774
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1681931Reviewed-by: Philip Rogers <pdr@chromium.org>
Commit-Queue: Xianzhu Wang <wangxianzhu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#673439}

third_party/blink/renderer/core/paint/paint_property_tree_builder.cc

@@ -169,6 +169,7 @@ class FragmentPaintPropertyTreeBuilder {
  private:
   ALWAYS_INLINE void UpdatePaintOffset();
   ALWAYS_INLINE void UpdateForPaintOffsetTranslation(base::Optional<IntPoint>&);
+  ALWAYS_INLINE bool IsAffectedByOuterViewportBoundsDelta() const;
   ALWAYS_INLINE void UpdatePaintOffsetTranslation(
       const base::Optional<IntPoint>&);
   ALWAYS_INLINE void SetNeedsPaintPropertyUpdateIfNeeded();
@@ -456,6 +457,18 @@ void FragmentPaintPropertyTreeBuilder::UpdateForPaintOffsetTranslation(
   context_.current.paint_offset = subpixel_accumulation;
 }
 
+bool FragmentPaintPropertyTreeBuilder::IsAffectedByOuterViewportBoundsDelta()
+    const {
+  if (object_.StyleRef().GetPosition() != EPosition::kFixed ||
+      !object_.StyleRef().IsFixedToBottom() ||
+      !object_.GetFrame()->IsMainFrame())
+    return false;
+
+  // It's affected by viewport only if the container is the LayoutView.
+  DCHECK_EQ(full_context_.container_for_fixed_position, object_.Container());
+  return full_context_.container_for_fixed_position->IsLayoutView();
+}
+
 void FragmentPaintPropertyTreeBuilder::UpdatePaintOffsetTranslation(
     const base::Optional<IntPoint>& paint_offset_translation) {
   DCHECK(properties_);
@@ -465,11 +478,8 @@ void FragmentPaintPropertyTreeBuilder::UpdatePaintOffsetTranslation(
         FloatSize(ToIntSize(*paint_offset_translation))};
     state.flattens_inherited_transform =
         context_.current.should_flatten_inherited_transform;
-
     state.affected_by_outer_viewport_bounds_delta =
-        object_.StyleRef().GetPosition() == EPosition::kFixed &&
-        object_.StyleRef().IsFixedToBottom();
-
+        IsAffectedByOuterViewportBoundsDelta();
     if (RuntimeEnabledFeatures::CompositeAfterPaintEnabled() ||
         RuntimeEnabledFeatures::BlinkGenPropertyTreesEnabled())
       state.rendering_context_id = context_.current.rendering_context_id;

third_party/blink/renderer/core/paint/paint_property_tree_builder_test.cc

@@ -6795,4 +6795,45 @@ TEST_P(PaintPropertyTreeBuilderTest, SetViewportScrollingBits) {
   }
 }
 
+TEST_P(PaintPropertyTreeBuilderTest, IsAffectedByOuterViewportBoundsDelta) {
+  SetBodyInnerHTML(R"HTML(
+    <style>div { will-change: transform; position: fixed; }</style>
+    <div id="fixed1"></div>
+    <div id="fixed2" style="right: 0"></div>
+    <div id="fixed3" style="bottom: 0"></div>
+    <div id="fixed4" style="bottom: 20px"></div>
+    <div style="transform: translateX(100px)">
+      <div id="fixed5" style="bottom: 0"></div>
+    </div>
+    <iframe></iframe>
+  )HTML");
+  SetChildFrameHTML(R"HTML(
+     <div id="fixed"
+          style="will-change: transform; position: fixed; bottom: 0"></div>
+  )HTML");
+  UpdateAllLifecyclePhasesForTest();
+
+  auto check_result = [&](const ObjectPaintProperties* properties,
+                          bool expected) {
+    ASSERT_TRUE(properties);
+    ASSERT_TRUE(properties->PaintOffsetTranslation());
+    EXPECT_EQ(expected, properties->PaintOffsetTranslation()
+                            ->IsAffectedByOuterViewportBoundsDelta());
+  };
+
+  check_result(PaintPropertiesForElement("fixed1"), false);
+  check_result(PaintPropertiesForElement("fixed2"), false);
+  check_result(PaintPropertiesForElement("fixed3"), true);
+  check_result(PaintPropertiesForElement("fixed4"), true);
+  check_result(PaintPropertiesForElement("fixed5"), false);
+
+  // Fixed elements in subframes are not affected by viewport.
+  check_result(ChildDocument()
+                   .getElementById("fixed")
+                   ->GetLayoutObject()
+                   ->FirstFragment()
+                   .PaintProperties(),
+               false);
+}
+
 }  // namespace blink