[blink-gen-property-trees] Skip viewport update pre-BGPT

Adding viewport nodes causes a performance regression so this CL turns
off the paint tree update in VisualViewport if BGPT (and SPv2) are off
since the nodes aren't needed.

Bug: 879205
Cq-Include-Trybots: luci.chromium.try:linux-blink-gen-property-trees;luci.chromium.try:linux_layout_tests_slimming_paint_v2;master.tryserver.blink:linux_trusty_blink_rel
Change-Id: I19060e1d487d50ac9b65ae7bdaa32dba2e5caaa7
Reviewed-on: https://chromium-review.googlesource.com/1228489Reviewed-by: Philip Rogers <pdr@chromium.org>
Commit-Queue: David Bokan <bokan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#592538}

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

@@ -447,9 +447,15 @@ TEST_P(PaintPropertyTreeBuilderTest, DocScrollingTraditional) {
   LocalFrameView* frame_view = GetDocument().View();
   frame_view->UpdateAllLifecyclePhases();
   EXPECT_EQ(TransformationMatrix(), DocPreTranslation()->Matrix());
+  if (RuntimeEnabledFeatures::SlimmingPaintV2Enabled() ||
+      RuntimeEnabledFeatures::BlinkGenPropertyTreesEnabled()) {
     EXPECT_EQ(
         GetDocument().GetPage()->GetVisualViewport().GetScrollTranslationNode(),
         DocPreTranslation()->Parent());
+  } else {
+    // Pre-BGPT we don't create the visual viewport property nodes.
+    EXPECT_TRUE(DocPreTranslation()->Parent()->IsRoot());
+  }
   EXPECT_EQ(TransformationMatrix().Translate(0, -100),
             DocScrollTranslation()->Matrix());
   EXPECT_EQ(DocPreTranslation(), DocScrollTranslation()->Parent());
@@ -3785,12 +3791,18 @@ TEST_P(PaintPropertyTreeBuilderTest, PositionedScrollerIsNotNested) {
   auto* fixed_overflow_scroll_node = fixed_scroll_translation->ScrollNode();
   // The fixed position overflow scroll node is parented under the root, not the
   // dom-order parent or frame's scroll.
+  if (RuntimeEnabledFeatures::SlimmingPaintV2Enabled() ||
+      RuntimeEnabledFeatures::BlinkGenPropertyTreesEnabled()) {
     EXPECT_EQ(GetDocument()
                   .GetPage()
                   ->GetVisualViewport()
                   .GetScrollTranslationNode()
                   ->ScrollNode(),
               fixed_overflow_scroll_node->Parent());
+  } else {
+    // Pre-BGPT we don't create the visual viewport property nodes.
+    EXPECT_TRUE(fixed_overflow_scroll_node->Parent()->IsRoot());
+  }
   EXPECT_EQ(TransformationMatrix().Translate(0, -43),
             fixed_scroll_translation->Matrix());
   EXPECT_EQ(IntRect(0, 0, 13, 11), fixed_overflow_scroll_node->ContainerRect());

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

@@ -268,12 +268,24 @@ TEST_P(PaintPropertyTreeUpdateTest,
                    ->ScrollTranslation()
                    ->ScrollNode()
                    ->HasBackgroundAttachmentFixedDescendants());
+  if (RuntimeEnabledFeatures::SlimmingPaintV2Enabled() ||
+      RuntimeEnabledFeatures::BlinkGenPropertyTreesEnabled()) {
     EXPECT_EQ(visual_viewport.GetScrollNode(), overflow_b->GetLayoutObject()
                                                    ->FirstFragment()
                                                    .PaintProperties()
                                                    ->ScrollTranslation()
                                                    ->ScrollNode()
                                                    ->Parent());
+  } else {
+    // Pre-BGPT we don't create the visual viewport property nodes.
+    EXPECT_TRUE(overflow_b->GetLayoutObject()
+                    ->FirstFragment()
+                    .PaintProperties()
+                    ->ScrollTranslation()
+                    ->ScrollNode()
+                    ->Parent()
+                    ->IsRoot());
+  }
 
   // Removing a main thread scrolling reason should update the entire tree.
   overflow_b->removeAttribute("class");
@@ -797,6 +809,11 @@ TEST_P(PaintPropertyTreeUpdateTest, ScrollBoundsChange) {
 // from the viewport's viewable area.
 TEST_P(PaintPropertyTreeUpdateTest,
        ViewportContentsAndContainerRectsIncludeScrollbar) {
+  // Pre-BGPT we don't create the visual viewport property nodes.
+  if (!RuntimeEnabledFeatures::SlimmingPaintV2Enabled() &&
+      !RuntimeEnabledFeatures::BlinkGenPropertyTreesEnabled())
+    return;
+
   SetBodyInnerHTML(R"HTML(
     <style>
       ::-webkit-scrollbar {width: 20px; height: 20px}

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

@@ -48,9 +48,12 @@ void PrePaintTreeWalk::WalkTree(LocalFrameView& root_frame_view) {
   if (needs_tree_builder_context_update)
     GeometryMapper::ClearCache();
 
+  if (RuntimeEnabledFeatures::BlinkGenPropertyTreesEnabled() ||
+      RuntimeEnabledFeatures::SlimmingPaintV2Enabled()) {
     VisualViewportPaintPropertyTreeBuilder::Update(
         root_frame_view.GetPage()->GetVisualViewport(),
         *context_storage_.back().tree_builder_context);
+  }
 
   Walk(root_frame_view);
   paint_invalidator_.ProcessPendingDelayedPaintInvalidations();