[CompositeAfterPaint] Don't composite during printing

This avoid unnecessary over-painting for composited layers (with cull
rects expanded by thousands of pixels) during printing.

This CL avoids some printing/ test failures due to expanded cull rects
when CullRectUpdate is enabled.

Bug: 1046544
Change-Id: I2f1582dcaf8a8ba91b9aa700ae459cf51a5dc935
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2724848
Reviewed-by: Philip Rogers <pdr@chromium.org>
Commit-Queue: Xianzhu Wang <wangxianzhu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#859064}

third_party/blink/renderer/core/paint/compositing/compositing_reason_finder.cc

@@ -122,6 +122,9 @@ static CompositingReasons BackfaceInvisibility3DAncestorReason(
 
 CompositingReasons CompositingReasonFinder::DirectReasonsForPaintProperties(
     const LayoutObject& object) {
+  if (object.GetDocument().Printing())
+    return CompositingReason::kNone;
+
   // TODO(wangxianzhu): Don't depend on PaintLayer for CompositeAfterPaint.
   if (!object.HasLayer()) {
     if (object.IsSVGChild())

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

@@ -5849,15 +5849,28 @@ TEST_P(PaintPropertyTreeBuilderTest, RepeatingFixedPositionInPagedMedia) {
   EXPECT_EQ(3u, NumFragments(fixed));
   for (int i = 0; i < 3; i++) {
     const auto& fragment = FragmentAt(fixed, i);
-    EXPECT_EQ(PhysicalOffset(0, 0), fragment.PaintOffset());
+    if (RuntimeEnabledFeatures::CompositeAfterPaintEnabled()) {
+      // In CompositeAfterPaint, we don't composite and create
+      // PaintOffsetTranslation for the fixed-position element during printing.
+      EXPECT_EQ(PhysicalOffset(20, 400 * i - 180), fragment.PaintOffset());
+      EXPECT_FALSE(fragment.PaintProperties());
+    } else {
+      // In pre-CompositeAfterPaint, we create PaintOffsetTranslation because
+      // the fixed-position element is currently composited.
+      EXPECT_EQ(PhysicalOffset(0, 0), fragment.PaintOffset());
+      EXPECT_EQ(FloatSize(20, 400 * i - 180), fragment.PaintProperties()
+                                                  ->PaintOffsetTranslation()
+                                                  ->Translation2D());
+    }
     EXPECT_EQ(LayoutUnit(400 * i), fragment.LogicalTopInFlowThread());
   }
 
   EXPECT_FALSE(fixed_child->IsFixedPositionObjectInPagedMedia());
   EXPECT_EQ(3u, NumFragments(fixed_child));
   for (int i = 0; i < 3; i++) {
     const auto& fragment = FragmentAt(fixed_child, i);
-    EXPECT_EQ(PhysicalOffset(0, 10), fragment.PaintOffset());
+    EXPECT_EQ(FragmentAt(fixed, i).PaintOffset() + PhysicalOffset(0, 10),
+              fragment.PaintOffset());
     EXPECT_EQ(LayoutUnit(i * 400), fragment.LogicalTopInFlowThread());
   }