Force subtree update when visual viewport adds/removes paint property nodes

This is like what we do for paint properties in the document.

Bug: 984881
Change-Id: Ib799e852017642d31de2616a5ebab554cbeb3770
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1752502Reviewed-by: Philip Rogers <pdr@chromium.org>
Commit-Queue: Xianzhu Wang <wangxianzhu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#686504}

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

@@ -101,6 +101,13 @@ PaintPropertyChangeType VisualViewportPaintPropertyTreeBuilder::Update(
   context.absolute_position.scroll = visual_viewport.GetScrollNode();
   context.fixed_position.scroll = visual_viewport.GetScrollNode();
 
+  if (property_changed >= PaintPropertyChangeType::kNodeAddedOrRemoved) {
+    // Force piercing subtree update for the worst case (scroll node added/
+    // removed). Not a big deal for performance because this is rare.
+    full_context.force_subtree_update_reasons |=
+        PaintPropertyTreeBuilderContext::kSubtreeUpdateIsolationPiercing;
+  }
+
 #if DCHECK_IS_ON()
   paint_property_tree_printer::UpdateDebugNames(visual_viewport);
 #endif

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

@@ -836,6 +836,60 @@ TEST_P(PaintPropertyTreeUpdateTest,
   EXPECT_EQ(IntSize(800, 600), visual_viewport.GetScrollNode()->ContentsSize());
 }
 
+TEST_P(PaintPropertyTreeUpdateTest, ViewportAddRemoveDeviceEmulationNode) {
+  SetBodyInnerHTML(
+      "<style>body {height: 10000px; width: 10000px; margin: 0;}</style>");
+
+  auto& visual_viewport = GetDocument().GetPage()->GetVisualViewport();
+  EXPECT_FALSE(visual_viewport.GetDeviceEmulationTransformNode());
+  // The LayoutView (instead of VisualViewport) creates scrollbars because
+  // viewport is disabled.
+  ASSERT_FALSE(GetDocument().GetPage()->GetSettings().GetViewportEnabled());
+  EXPECT_FALSE(visual_viewport.LayerForHorizontalScrollbar());
+  EXPECT_FALSE(visual_viewport.LayerForVerticalScrollbar());
+  auto* scrollbar_layer =
+      GetLayoutView().GetScrollableArea()->LayerForHorizontalScrollbar();
+  if (!RuntimeEnabledFeatures::CompositeAfterPaintEnabled()) {
+    ASSERT_TRUE(scrollbar_layer);
+    EXPECT_EQ(&TransformPaintPropertyNode::Root(),
+              &scrollbar_layer->GetPropertyTreeState().Transform());
+  } else {
+    // TODO(wangxianzhu): Test for CompositeAfterPaint.
+    EXPECT_FALSE(scrollbar_layer);
+  }
+
+  // These emulate WebViewImpl::SetDeviceEmulationTransform().
+  GetChromeClient().SetDeviceEmulationTransform(
+      TransformationMatrix().Scale(2));
+  visual_viewport.SetNeedsPaintPropertyUpdate();
+
+  UpdateAllLifecyclePhasesForTest();
+  EXPECT_TRUE(visual_viewport.GetDeviceEmulationTransformNode());
+  if (!RuntimeEnabledFeatures::CompositeAfterPaintEnabled()) {
+    ASSERT_TRUE(scrollbar_layer);
+    EXPECT_EQ(visual_viewport.GetDeviceEmulationTransformNode(),
+              &scrollbar_layer->GetPropertyTreeState().Transform());
+  } else {
+    // TODO(wangxianzhu): Test for CompositeAfterPaint.
+    EXPECT_FALSE(scrollbar_layer);
+  }
+
+  // These emulate WebViewImpl::SetDeviceEmulationTransform().
+  GetChromeClient().SetDeviceEmulationTransform(TransformationMatrix());
+  visual_viewport.SetNeedsPaintPropertyUpdate();
+
+  UpdateAllLifecyclePhasesForTest();
+  EXPECT_FALSE(visual_viewport.GetDeviceEmulationTransformNode());
+  if (!RuntimeEnabledFeatures::CompositeAfterPaintEnabled()) {
+    ASSERT_TRUE(scrollbar_layer);
+    EXPECT_EQ(&TransformPaintPropertyNode::Root(),
+              &scrollbar_layer->GetPropertyTreeState().Transform());
+  } else {
+    // TODO(wangxianzhu): Test for CompositeAfterPaint.
+    EXPECT_FALSE(scrollbar_layer);
+  }
+}
+
 TEST_P(PaintPropertyTreeUpdateTest, ScrollbarWidthChange) {
   SetBodyInnerHTML(R"HTML(
     <style>::-webkit-scrollbar {width: 20px; height: 20px}</style>

third_party/blink/renderer/core/testing/core_unit_test_helper.h

@@ -89,8 +89,16 @@ class RenderingTestChromeClient : public EmptyChromeClient {
     return layer_tree_->layer_tree_host();
   }
 
+  void SetDeviceEmulationTransform(const TransformationMatrix& t) {
+    device_emulation_transform_ = t;
+  }
+  TransformationMatrix GetDeviceEmulationTransform() const override {
+    return device_emulation_transform_;
+  }
+
  private:
   std::unique_ptr<LayerTreeHostEmbedder> layer_tree_;
+  TransformationMatrix device_emulation_transform_;
 };
 
 class RenderingTest : public PageTestBase, public UseMockScrollbarSettings {