Use background color smaller than previous ones but big enough

In the following case
 <div style="will-change: transform; width: 300px; height: 300px; background: blue">
   <div style="width: 250px; height: 250px; background: green"></div>
 </div>
we'll use green as the background color instead of blue. Though the
green background is smaller than the blue background, green affects
more area than blue.

Bug: 1143099
Change-Id: I5032c0448a827c8ddf9e97d460147227e8a0fed2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2508292Reviewed-by: Stefan Zager <szager@chromium.org>
Commit-Queue: Xianzhu Wang <wangxianzhu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#823731}

third_party/blink/renderer/platform/graphics/compositing/paint_chunks_to_cc_layer.cc

@@ -800,36 +800,41 @@ scoped_refptr<cc::DisplayItemList> PaintChunksToCcLayer::Convert(
 
 // The heuristic for picking a checkerboarding color works as follows:
 //   - During paint, PaintChunker will look for background color display items,
-//     and annotates the chunk with the index of the display item that paints
-//     the largest area background color (ties are broken by selecting the
-//     display item that paints last).
+//     and record the background color of the latest display item with the
+//     largest background or bigger a ratio of the chunk bounds.
 //   - After layer allocation, the paint chunks assigned to a layer are
-//     examined for a background color annotation. The chunk with the largest
-//     background color annotation is selected.
-//   - If the area of the selected background color is at least half the size
-//     of the layer, then it is set as the layer's background color.
-//   - The same color is used for the layer's safe opaque background color, but
-//     without the size requirement, as safe opaque background color should
-//     always get a value if possible.
+//     examined for a background color annotation.
+//   - The background color of the latest chunk with a background larger than
+//     a ratio of the layer is set as the layer's background color.
+//   - If the above color exists, it's also used as the safe opaque background
+//     color. Otherwise the color of the largest background is used, without the
+//     size requirement, as safe opaque background color should always get a
+//     value if possible.
 static void UpdateBackgroundColor(cc::Layer& layer,
                                   const PaintChunkSubset& paint_chunks) {
-  SkColor color = SK_ColorTRANSPARENT;
-  uint64_t area = 0;
-  for (const auto& chunk : paint_chunks) {
-    if (chunk.background_color != Color::kTransparent &&
-        chunk.background_color_area >= area) {
-      color = chunk.background_color.Rgb();
-      area = chunk.background_color_area;
+  SkColor background_color = SK_ColorTRANSPARENT;
+  SkColor safe_opaque_background_color = SK_ColorTRANSPARENT;
+  float safe_opaque_background_area = 0;
+  float min_background_area = kMinBackgroundColorCoverageRatio *
+                              layer.bounds().width() * layer.bounds().height();
+  for (auto it = paint_chunks.end(); it != paint_chunks.begin();) {
+    const auto& chunk = *(--it);
+    if (chunk.background_color == Color::kTransparent)
+      continue;
+    if (chunk.background_color_area >= min_background_area) {
+      background_color = chunk.background_color.Rgb();
+      safe_opaque_background_color = background_color;
+      break;
+    }
+    if (chunk.background_color_area >= safe_opaque_background_area) {
+      // This color will be used only if we don't find proper background_color.
+      safe_opaque_background_color = chunk.background_color.Rgb();
+      safe_opaque_background_area = chunk.background_color_area;
     }
   }
 
-  layer.SetSafeOpaqueBackgroundColor(color);
-
-  uint64_t layer_area =
-      static_cast<uint64_t>(layer.bounds().width()) * layer.bounds().height();
-  if (area < layer_area / 2)
-    color = SK_ColorTRANSPARENT;
-  layer.SetBackgroundColor(color);
+  layer.SetBackgroundColor(background_color);
+  layer.SetSafeOpaqueBackgroundColor(safe_opaque_background_color);
 }
 
 static void UpdateTouchActionRegion(

third_party/blink/renderer/platform/graphics/paint/drawing_display_item.cc

@@ -78,7 +78,7 @@ bool DrawingDisplayItem::Equals(const DisplayItem& other) const {
   return BitmapsEqual(std::move(record), std::move(other_record), bounds);
 }
 
-SkColor DrawingDisplayItem::BackgroundColor(uint64_t& area) const {
+SkColor DrawingDisplayItem::BackgroundColor(float& area) const {
   if (GetType() != DisplayItem::kBoxDecorationBackground &&
       GetType() != DisplayItem::kDocumentBackground &&
       GetType() != DisplayItem::kDocumentRootBackdrop)
@@ -111,8 +111,7 @@ SkColor DrawingDisplayItem::BackgroundColor(uint64_t& area) const {
       default:
         continue;
     }
-    area =
-        base::saturated_cast<uint64_t>(item_rect.width() * item_rect.height());
+    area = item_rect.width() * item_rect.height();
     return flags.getColor();
   }
   return SK_ColorTRANSPARENT;

third_party/blink/renderer/platform/graphics/paint/drawing_display_item.h

@@ -51,7 +51,7 @@ class PLATFORM_EXPORT DrawingDisplayItem : public DisplayItem {
     known_to_be_opaque_ = true;
   }
 
-  SkColor BackgroundColor(uint64_t& area) const;
+  SkColor BackgroundColor(float& area) const;
 
  private:
   bool CalculateKnownToBeOpaque(const PaintRecord*) const;

third_party/blink/renderer/platform/graphics/paint/paint_chunk.cc

@@ -14,7 +14,7 @@ struct SameSizeAsPaintChunk {
   wtf_size_t begin_index;
   wtf_size_t end_index;
   Color background_color;
-  uint64_t background_color_area;
+  float background_color_area;
   PaintChunk::Id id;
   PropertyTreeState properties;
   IntRect bounds;

third_party/blink/renderer/platform/graphics/paint/paint_chunk.h

@@ -19,6 +19,8 @@
 
 namespace blink {
 
+constexpr float kMinBackgroundColorCoverageRatio = 0.5;
+
 // A contiguous sequence of drawings with common paint properties.
 //
 // This is expected to be owned by the paint artifact which also owns the
@@ -113,7 +115,7 @@ struct PLATFORM_EXPORT PaintChunk {
   Color background_color;
 
   // The area that is painted by the paint op that defines background_color.
-  uint64_t background_color_area;
+  float background_color_area;
 
   // Identifier of this chunk. It should be unique if |is_cacheable| is true.
   // This is used to match a new chunk to a cached old chunk to track changes

third_party/blink/renderer/platform/graphics/paint/paint_chunk_subset.h

@@ -60,6 +60,10 @@ class PaintChunkSubset {
       ++subset_or_chunk_index_;
       return *this;
     }
+    const Iterator& operator--() {
+      --subset_or_chunk_index_;
+      return *this;
+    }
     Iterator operator+(wtf_size_t offset) const {
       DCHECK_LE(subset_or_chunk_index_ + offset,
                 subset_.end().subset_or_chunk_index_);

third_party/blink/renderer/platform/graphics/paint/paint_chunker.cc

@@ -98,7 +98,7 @@ bool PaintChunker::IncrementDisplayItemIndex(const DisplayItem& item) {
   // If this paints the background and it's larger than our current candidate,
   // set the candidate to be this item.
   if (item.IsDrawing() && item.DrawsContent()) {
-    uint64_t item_area;
+    float item_area;
     Color item_color =
         static_cast<const DrawingDisplayItem&>(item).BackgroundColor(item_area);
     ProcessBackgroundColorCandidate(chunk.id, item_color, item_area);
@@ -188,11 +188,13 @@ void PaintChunker::CreateScrollHitTestChunk(
 
 bool PaintChunker::ProcessBackgroundColorCandidate(const PaintChunk::Id& id,
                                                    Color color,
-                                                   uint64_t area) {
+                                                   float area) {
   bool created_new_chunk = EnsureCurrentChunk(id);
   if (color != Color::kTransparent &&
-      (candidate_background_color_ == Color::kTransparent ||
-       (area >= candidate_background_area_))) {
+      (area >= candidate_background_area_ ||
+       area >= kMinBackgroundColorCoverageRatio *
+                   chunks_->back().bounds.Width() *
+                   chunks_->back().bounds.Height())) {
     candidate_background_color_ = color;
     candidate_background_area_ = area;
   }

third_party/blink/renderer/platform/graphics/paint/paint_chunker.h

@@ -71,7 +71,7 @@ class PLATFORM_EXPORT PaintChunker final {
   // Returns true if a new chunk is created.
   bool ProcessBackgroundColorCandidate(const PaintChunk::Id& id,
                                        Color color,
-                                       uint64_t area);
+                                       float area);
 
   // Returns true if a new chunk is created.
   bool EnsureChunk() { return EnsureCurrentChunk(*next_chunk_id_); }
@@ -103,7 +103,7 @@ class PLATFORM_EXPORT PaintChunker final {
   bool will_force_new_chunk_ = true;
 
   Color candidate_background_color_ = Color::kTransparent;
-  uint64_t candidate_background_area_ = 0;
+  float candidate_background_area_ = 0;
 
   DISALLOW_COPY_AND_ASSIGN(PaintChunker);
 };

third_party/blink/web_tests/compositing/background-color/background-color-coverage-expected.txt

+{
+  "layers": [
+    {
+      "name": "Scrolling Contents Layer",
+      "bounds": [785, 628],
+      "contentsOpaque": true,
+      "backgroundColor": "#FFFFFF"
+    },
+    {
+      "name": "LayoutNGBlockFlow (positioned) DIV id='target'",
+      "bounds": [620, 620],
+      "contentsOpaque": true,
+      "backgroundColor": "#008000",
+      "transform": 1
+    },
+    {
+      "name": "ContentsLayer for Vertical Scrollbar Layer",
+      "position": [785, 0],
+      "bounds": [15, 600],
+      "contentsOpaque": true
+    }
+  ],
+  "transforms": [
+    {
+      "id": 1,
+      "transform": [
+        [1, 0, 0, 0],
+        [0, 1, 0, 0],
+        [0, 0, 1, 0],
+        [8, 8, 0, 1]
+      ]
+    }
+  ]
+}
+

third_party/blink/web_tests/compositing/background-color/background-color-coverage.html

+<!DOCTYPE html>
+<script>
+onload = () => {
+  if (window.testRunner && window.internals) {
+    testRunner.dumpAsText();
+    testRunner.setCustomTextOutput(internals.layerTreeAsText(document));
+  }
+}
+</script>
+<div id="target" style="background: hotpink; padding: 10px; will-change: transform; position: absolute">
+  <div style="background: green; padding: 200px">
+    <div style="background: red; width: 200px; height: 200px"></div>
+  </div>
+</div>

third_party/blink/web_tests/compositing/force-compositing-mode/overflow-hidden-iframe-layer-expected.txt

@@ -4,7 +4,7 @@
       "name": "Scrolling Contents Layer",
       "bounds": [800, 600],
       "contentsOpaque": true,
-      "backgroundColor": "#FFFFFF"
+      "backgroundColor": "#0000FF"
     }
   ]
 }

third_party/blink/web_tests/compositing/overflow/overflow-visible-with-touch-expected.txt

@@ -4,7 +4,7 @@
       "name": "Scrolling Contents Layer",
       "bounds": [1008, 1008],
       "contentsOpaque": true,
-      "backgroundColor": "#FFFFFF"
+      "backgroundColor": "#C0C0C0"
     },
     {
       "name": "ContentsLayer for Horizontal Scrollbar Layer",

third_party/blink/web_tests/compositing/overflow/scrollbar-layer-placement-expected.txt

@@ -23,7 +23,7 @@
       "position": [5, 5],
       "bounds": [220, 236],
       "contentsOpaque": true,
-      "backgroundColor": "#FFFFFF",
+      "backgroundColor": "#DDDDDD",
       "transform": 2
     },
     {
@@ -49,7 +49,7 @@
       "position": [5, 5],
       "bounds": [220, 236],
       "contentsOpaque": true,
-      "backgroundColor": "#FFFFFF",
+      "backgroundColor": "#DDDDDD",
       "transform": 4
     },
     {
@@ -75,7 +75,7 @@
       "position": [5, 5],
       "bounds": [220, 236],
       "contentsOpaque": true,
-      "backgroundColor": "#FFFFFF",
+      "backgroundColor": "#DDDDDD",
       "transform": 6
     },
     {
@@ -101,7 +101,7 @@
       "position": [5, 5],
       "bounds": [220, 236],
       "contentsOpaque": true,
-      "backgroundColor": "#FFFFFF",
+      "backgroundColor": "#DDDDDD",
       "transform": 8
     },
     {

third_party/blink/web_tests/compositing/squashing/no-squashing-into-fixed-position-that-clips-expected.txt

@@ -4,7 +4,7 @@
       "name": "Scrolling Contents Layer",
       "bounds": [800, 600],
       "contentsOpaque": true,
-      "backgroundColor": "#FFFFFF"
+      "backgroundColor": "#ADD8E6"
     },
     {
       "name": "LayoutNGBlockFlow (positioned) DIV class='compositedlayer'",

third_party/blink/web_tests/flag-specific/composite-after-paint/compositing/background-color/background-color-coverage-expected.txt

+{
+  "layers": [
+    {
+      "name": "Scrolling background of LayoutView #document",
+      "bounds": [785, 628],
+      "contentsOpaque": true,
+      "backgroundColor": "#FFFFFF"
+    },
+    {
+      "name": "LayoutNGBlockFlow (positioned) DIV id='target'",
+      "bounds": [620, 620],
+      "contentsOpaque": true,
+      "backgroundColor": "#008000",
+      "transform": 1
+    },
+    {
+      "name": "VerticalScrollbar",
+      "position": [785, 0],
+      "bounds": [15, 600]
+    }
+  ],
+  "transforms": [
+    {
+      "id": 1,
+      "transform": [
+        [1, 0, 0, 0],
+        [0, 1, 0, 0],
+        [0, 0, 1, 0],
+        [8, 8, 0, 1]
+      ]
+    }
+  ]
+}
+

third_party/blink/web_tests/flag-specific/composite-after-paint/compositing/force-compositing-mode/overflow-hidden-iframe-layer-expected.txt

@@ -4,7 +4,7 @@
       "name": "Scrolling background of LayoutView #document",
       "bounds": [800, 600],
       "contentsOpaque": true,
-      "backgroundColor": "#FFFFFF"
+      "backgroundColor": "#0000FF"
     }
   ]
 }

third_party/blink/web_tests/flag-specific/composite-after-paint/compositing/overflow/overflow-visible-with-touch-expected.txt

@@ -4,7 +4,7 @@
       "name": "Scrolling background of LayoutView #document",
       "bounds": [1008, 1008],
       "contentsOpaque": true,
-      "backgroundColor": "#FFFFFF"
+      "backgroundColor": "#C0C0C0"
     },
     {
       "name": "HorizontalScrollbar",

third_party/blink/web_tests/flag-specific/composite-after-paint/compositing/overflow/scrollbar-layer-placement-expected.txt

@@ -23,7 +23,7 @@
       "name": "LayoutNGBlockFlow (relative positioned) DIV class='scroller'",
       "position": [5, 5],
       "bounds": [220, 236],
-      "backgroundColor": "#FFFFFF",
+      "backgroundColor": "#DDDDDD",
       "transform": 2
     },
     {
@@ -49,7 +49,7 @@
       "name": "LayoutNGBlockFlow DIV class='scroller'",
       "position": [5, 5],
       "bounds": [220, 236],
-      "backgroundColor": "#FFFFFF",
+      "backgroundColor": "#DDDDDD",
       "transform": 4
     },
     {
@@ -75,7 +75,7 @@
       "name": "LayoutNGBlockFlow DIV class='scroller'",
       "position": [5, 5],
       "bounds": [220, 236],
-      "backgroundColor": "#FFFFFF",
+      "backgroundColor": "#DDDDDD",
       "transform": 6
     },
     {
@@ -101,7 +101,7 @@
       "name": "LayoutNGBlockFlow DIV class='scroller'",
       "position": [5, 5],
       "bounds": [220, 236],
-      "backgroundColor": "#FFFFFF",
+      "backgroundColor": "#DDDDDD",
       "transform": 8
     },
     {

third_party/blink/web_tests/flag-specific/composite-after-paint/paint/invalidation/canvas-resize-no-full-invalidation-expected.txt

@@ -4,7 +4,7 @@
       "name": "Scrolling background of LayoutView #document",
       "bounds": [800, 600],
       "contentsOpaque": true,
-      "backgroundColor": "#FFFFFF",
+      "backgroundColor": "#003300",
       "invalidations": [
         [550, 50, 100, 500]
       ]

third_party/blink/web_tests/flag-specific/composite-after-paint/paint/invalidation/clip/css-clip-change-stacking-child-expected.txt

@@ -4,7 +4,7 @@
       "name": "Scrolling background of LayoutView #document",
       "bounds": [800, 600],
       "contentsOpaque": true,
-      "backgroundColor": "#FFFFFF",
+      "backgroundColor": "#ADD8E6",
       "invalidations": [
         [8, 208, 300, 100]
       ]

third_party/blink/web_tests/flag-specific/composite-after-paint/paint/invalidation/clip/mask-clip-change-stacking-child-expected.txt

@@ -4,7 +4,7 @@
       "name": "Scrolling background of LayoutView #document",
       "bounds": [800, 600],
       "contentsOpaque": true,
-      "backgroundColor": "#FFFFFF",
+      "backgroundColor": "#ADD8E6",
       "invalidations": [
         [8, 8, 300, 300]
       ]

third_party/blink/web_tests/flag-specific/composite-after-paint/paint/invalidation/compositing/should-not-clip-composited-viewport-scrolling-layer-expected.txt

@@ -4,7 +4,7 @@
       "name": "Scrolling background of LayoutView #document",
       "bounds": [2008, 1516],
       "contentsOpaque": true,
-      "backgroundColor": "#FFFFFF",
+      "backgroundColor": "#008000",
       "invalidations": [
         [8, 8, 2000, 1500]
       ],

third_party/blink/web_tests/flag-specific/composite-after-paint/paint/invalidation/multicol/multicol-with-overflowing-block-rl-expected.txt

@@ -4,7 +4,7 @@
       "name": "Scrolling background of LayoutView #document",
       "bounds": [800, 600],
       "contentsOpaque": true,
-      "backgroundColor": "#FFFFFF",
+      "backgroundColor": "#008000",
       "invalidations": [
         [8, 174, 500, 168],
         [8, 341, 500, 167],

third_party/blink/web_tests/flag-specific/composite-after-paint/paint/invalidation/overflow/resize-child-within-overflow-expected.txt

@@ -4,7 +4,7 @@
       "name": "Scrolling background of LayoutView #document",
       "bounds": [800, 1000],
       "contentsOpaque": true,
-      "backgroundColor": "#FFFFFF",
+      "backgroundColor": "#0000FF",
       "invalidations": [
         [400, 0, 200, 1000]
       ]

third_party/blink/web_tests/flag-specific/composite-after-paint/paint/invalidation/reflection/scroll-fixed-reflected-layer-expected.txt

@@ -10,7 +10,7 @@
     {
       "name": "LayoutNGBlockFlow (positioned) DIV class='reflected fixed'",
       "bounds": [100, 100],
-      "backgroundColor": "#FF0000",
+      "backgroundColor": "#008000",
       "invalidations": [
         [0, 0, 100, 100]
       ],

third_party/blink/web_tests/flag-specific/composite-after-paint/paint/invalidation/scroll/document-flipped-blocks-writing-mode-scroll-expected.txt

@@ -4,7 +4,7 @@
       "name": "Scrolling background of LayoutView #document",
       "bounds": [1516, 585],
       "contentsOpaque": true,
-      "backgroundColor": "#008000"
+      "backgroundColor": "#ADD8E6"
     },
     {
       "name": "HorizontalScrollbar",

third_party/blink/web_tests/flag-specific/composite-after-paint/paint/invalidation/scroll/scrolled-iframe-scrollbar-change-expected.txt

@@ -4,7 +4,7 @@
       "name": "Scrolling background of LayoutView #document",
       "bounds": [804, 604],
       "contentsOpaque": true,
-      "backgroundColor": "#FF0000",
+      "backgroundColor": "#008000",
       "invalidations": [
         [2, 2, 800, 600]
       ]

third_party/blink/web_tests/flag-specific/composite-after-paint/paint/invalidation/selection/selection-within-composited-scroller-expected.txt

@@ -22,7 +22,7 @@
       "name": "LayoutNGBlockFlow DIV id='scroller'",
       "bounds": [200, 1620],
       "contentsOpaque": true,
-      "backgroundColor": "#D3D3D3",
+      "backgroundColor": "#ADD8E6",
       "invalidations": [
         [0, 610, 22, 20]
       ],

third_party/blink/web_tests/flag-specific/composite-after-paint/paint/invalidation/table/scroll-inside-table-cell-expected.txt

@@ -4,7 +4,7 @@
       "name": "Scrolling background of LayoutView #document",
       "bounds": [800, 600],
       "contentsOpaque": true,
-      "backgroundColor": "#FFFFFF",
+      "backgroundColor": "#FF0000",
       "invalidations": [
         [314, 114, 435, 450],
         [314, 564, 435, 15]

third_party/blink/web_tests/flag-specific/composite-after-paint/paint/invalidation/window-resize/window-resize-no-layout-change1-expected.txt

@@ -4,7 +4,7 @@
       "name": "Scrolling background of LayoutView #document",
       "bounds": [2008, 2016],
       "contentsOpaque": true,
-      "backgroundColor": "#FFFFFF"
+      "backgroundColor": "#0000FF"
     }
   ]
 }
@@ -14,7 +14,7 @@
       "name": "Scrolling background of LayoutView #document",
       "bounds": [2008, 2016],
       "contentsOpaque": true,
-      "backgroundColor": "#FFFFFF"
+      "backgroundColor": "#0000FF"
     }
   ]
 }
@@ -24,7 +24,7 @@
       "name": "Scrolling background of LayoutView #document",
       "bounds": [2008, 2016],
       "contentsOpaque": true,
-      "backgroundColor": "#FFFFFF"
+      "backgroundColor": "#0000FF"
     }
   ]
 }
@@ -34,7 +34,7 @@
       "name": "Scrolling background of LayoutView #document",
       "bounds": [2008, 2016],
       "contentsOpaque": true,
-      "backgroundColor": "#FFFFFF"
+      "backgroundColor": "#0000FF"
     }
   ]
 }

third_party/blink/web_tests/flag-specific/composite-after-paint/paint/invalidation/window-resize/window-resize-no-layout-change2-expected.txt

@@ -4,7 +4,7 @@
       "name": "Scrolling background of LayoutView #document",
       "bounds": [2008, 2008],
       "contentsOpaque": true,
-      "backgroundColor": "#FFFFFF"
+      "backgroundColor": "#0000FF"
     }
   ]
 }
@@ -14,7 +14,7 @@
       "name": "Scrolling background of LayoutView #document",
       "bounds": [2008, 2008],
       "contentsOpaque": true,
-      "backgroundColor": "#FFFFFF"
+      "backgroundColor": "#0000FF"
     }
   ]
 }
@@ -24,7 +24,7 @@
       "name": "Scrolling background of LayoutView #document",
       "bounds": [2008, 2008],
       "contentsOpaque": true,
-      "backgroundColor": "#FFFFFF"
+      "backgroundColor": "#0000FF"
     }
   ]
 }
@@ -34,7 +34,7 @@
       "name": "Scrolling background of LayoutView #document",
       "bounds": [2008, 2008],
       "contentsOpaque": true,
-      "backgroundColor": "#FFFFFF"
+      "backgroundColor": "#0000FF"
     }
   ]
 }

third_party/blink/web_tests/flag-specific/disable-layout-ng/compositing/background-color/background-color-coverage-expected.txt

+{
+  "layers": [
+    {
+      "name": "Scrolling Contents Layer",
+      "bounds": [785, 628],
+      "contentsOpaque": true,
+      "backgroundColor": "#FFFFFF"
+    },
+    {
+      "name": "LayoutBlockFlow (positioned) DIV id='target'",
+      "bounds": [620, 620],
+      "contentsOpaque": true,
+      "backgroundColor": "#008000",
+      "transform": 1
+    },
+    {
+      "name": "ContentsLayer for Vertical Scrollbar Layer",
+      "position": [785, 0],
+      "bounds": [15, 600],
+      "contentsOpaque": true
+    }
+  ],
+  "transforms": [
+    {
+      "id": 1,
+      "transform": [
+        [1, 0, 0, 0],
+        [0, 1, 0, 0],
+        [0, 0, 1, 0],
+        [8, 8, 0, 1]
+      ]
+    }
+  ]
+}
+

third_party/blink/web_tests/flag-specific/disable-layout-ng/compositing/overflow/scrollbar-layer-placement-expected.txt

@@ -23,7 +23,7 @@
       "position": [5, 5],
       "bounds": [220, 236],
       "contentsOpaque": true,
-      "backgroundColor": "#FFFFFF",
+      "backgroundColor": "#DDDDDD",
       "transform": 2
     },
     {
@@ -49,7 +49,7 @@
       "position": [5, 5],
       "bounds": [220, 236],
       "contentsOpaque": true,
-      "backgroundColor": "#FFFFFF",
+      "backgroundColor": "#DDDDDD",
       "transform": 4
     },
     {
@@ -75,7 +75,7 @@
       "position": [5, 5],
       "bounds": [220, 236],
       "contentsOpaque": true,
-      "backgroundColor": "#FFFFFF",
+      "backgroundColor": "#DDDDDD",
       "transform": 6
     },
     {
@@ -101,7 +101,7 @@
       "position": [5, 5],
       "bounds": [220, 236],
       "contentsOpaque": true,
-      "backgroundColor": "#FFFFFF",
+      "backgroundColor": "#DDDDDD",
       "transform": 8
     },
     {

third_party/blink/web_tests/flag-specific/disable-layout-ng/compositing/squashing/no-squashing-into-fixed-position-that-clips-expected.txt

@@ -4,7 +4,7 @@
       "name": "Scrolling Contents Layer",
       "bounds": [800, 600],
       "contentsOpaque": true,
-      "backgroundColor": "#FFFFFF"
+      "backgroundColor": "#ADD8E6"
     },
     {
       "name": "LayoutBlockFlow (positioned) DIV class='compositedlayer'",

third_party/blink/web_tests/flag-specific/disable-layout-ng/paint/invalidation/reflection/scroll-fixed-reflected-layer-expected.txt

@@ -11,7 +11,7 @@
       "name": "LayoutBlockFlow (positioned) DIV class='reflected fixed'",
       "bounds": [100, 100],
       "contentsOpaque": true,
-      "backgroundColor": "#FF0000",
+      "backgroundColor": "#008000",
       "invalidations": [
         [0, 0, 100, 100]
       ],

third_party/blink/web_tests/flag-specific/disable-layout-ng/paint/invalidation/selection/selection-within-composited-scroller-expected.txt

@@ -33,7 +33,7 @@
       "name": "Scrolling Contents Layer",
       "bounds": [200, 1620],
       "contentsOpaque": true,
-      "backgroundColor": "#D3D3D3",
+      "backgroundColor": "#ADD8E6",
       "invalidations": [
         [0, 610, 22, 19]
       ],

third_party/blink/web_tests/paint/invalidation/canvas-resize-no-full-invalidation-expected.txt

@@ -4,7 +4,7 @@
       "name": "Scrolling Contents Layer",
       "bounds": [800, 600],
       "contentsOpaque": true,
-      "backgroundColor": "#FFFFFF",
+      "backgroundColor": "#003300",
       "invalidations": [
         [550, 50, 100, 500]
       ]

third_party/blink/web_tests/paint/invalidation/clip/css-clip-change-stacking-child-expected.txt

@@ -4,7 +4,7 @@
       "name": "Scrolling Contents Layer",
       "bounds": [800, 600],
       "contentsOpaque": true,
-      "backgroundColor": "#FFFFFF",
+      "backgroundColor": "#ADD8E6",
       "invalidations": [
         [8, 208, 300, 100]
       ]

third_party/blink/web_tests/paint/invalidation/clip/mask-clip-change-stacking-child-expected.txt

@@ -4,7 +4,7 @@
       "name": "Scrolling Contents Layer",
       "bounds": [800, 600],
       "contentsOpaque": true,
-      "backgroundColor": "#FFFFFF",
+      "backgroundColor": "#ADD8E6",
       "invalidations": [
         [8, 8, 300, 300]
       ]

third_party/blink/web_tests/paint/invalidation/compositing/should-not-clip-composited-viewport-scrolling-layer-expected.txt

@@ -4,7 +4,7 @@
       "name": "Scrolling Contents Layer",
       "bounds": [2008, 1516],
       "contentsOpaque": true,
-      "backgroundColor": "#FFFFFF",
+      "backgroundColor": "#008000",
       "invalidations": [
         [8, 8, 2000, 1500]
       ],

third_party/blink/web_tests/paint/invalidation/multicol/multicol-with-overflowing-block-rl-expected.txt

@@ -4,7 +4,7 @@
       "name": "Scrolling Contents Layer",
       "bounds": [800, 600],
       "contentsOpaque": true,
-      "backgroundColor": "#FFFFFF",
+      "backgroundColor": "#008000",
       "invalidations": [
         [8, 174, 500, 168],
         [8, 341, 500, 167],

third_party/blink/web_tests/paint/invalidation/overflow/resize-child-within-overflow-expected.txt

@@ -4,7 +4,7 @@
       "name": "Scrolling Contents Layer",
       "bounds": [800, 1000],
       "contentsOpaque": true,
-      "backgroundColor": "#FFFFFF",
+      "backgroundColor": "#0000FF",
       "invalidations": [
         [400, 0, 200, 1000]
       ]

third_party/blink/web_tests/paint/invalidation/reflection/scroll-fixed-reflected-layer-expected.txt

@@ -11,7 +11,7 @@
       "name": "LayoutNGBlockFlow (positioned) DIV class='reflected fixed'",
       "bounds": [100, 100],
       "contentsOpaque": true,
-      "backgroundColor": "#FF0000",
+      "backgroundColor": "#008000",
       "invalidations": [
         [0, 0, 100, 100]
       ],

third_party/blink/web_tests/paint/invalidation/scroll/document-flipped-blocks-writing-mode-scroll-expected.txt

@@ -4,7 +4,7 @@
       "name": "Scrolling Contents Layer",
       "bounds": [1516, 585],
       "contentsOpaque": true,
-      "backgroundColor": "#008000"
+      "backgroundColor": "#ADD8E6"
     },
     {
       "name": "ContentsLayer for Horizontal Scrollbar Layer",

third_party/blink/web_tests/paint/invalidation/scroll/scrolled-iframe-scrollbar-change-expected.txt

@@ -4,7 +4,7 @@
       "name": "Scrolling Contents Layer",
       "bounds": [804, 604],
       "contentsOpaque": true,
-      "backgroundColor": "#FF0000",
+      "backgroundColor": "#008000",
       "invalidations": [
         [2, 2, 800, 600]
       ]

third_party/blink/web_tests/paint/invalidation/window-resize/window-resize-no-layout-change1-expected.txt

@@ -4,7 +4,7 @@
       "name": "Scrolling Contents Layer",
       "bounds": [2008, 2016],
       "contentsOpaque": true,
-      "backgroundColor": "#FFFFFF"
+      "backgroundColor": "#0000FF"
     }
   ]
 }
@@ -14,7 +14,7 @@
       "name": "Scrolling Contents Layer",
       "bounds": [2008, 2016],
       "contentsOpaque": true,
-      "backgroundColor": "#FFFFFF"
+      "backgroundColor": "#0000FF"
     }
   ]
 }
@@ -24,7 +24,7 @@
       "name": "Scrolling Contents Layer",
       "bounds": [2008, 2016],
       "contentsOpaque": true,
-      "backgroundColor": "#FFFFFF"
+      "backgroundColor": "#0000FF"
     }
   ]
 }
@@ -34,7 +34,7 @@
       "name": "Scrolling Contents Layer",
       "bounds": [2008, 2016],
       "contentsOpaque": true,
-      "backgroundColor": "#FFFFFF"
+      "backgroundColor": "#0000FF"
     }
   ]
 }

third_party/blink/web_tests/paint/invalidation/window-resize/window-resize-no-layout-change2-expected.txt

@@ -4,7 +4,7 @@
       "name": "Scrolling Contents Layer",
       "bounds": [2008, 2008],
       "contentsOpaque": true,
-      "backgroundColor": "#FFFFFF"
+      "backgroundColor": "#0000FF"
     }
   ]
 }
@@ -14,7 +14,7 @@
       "name": "Scrolling Contents Layer",
       "bounds": [2008, 2008],
       "contentsOpaque": true,
-      "backgroundColor": "#FFFFFF"
+      "backgroundColor": "#0000FF"
     }
   ]
 }
@@ -24,7 +24,7 @@
       "name": "Scrolling Contents Layer",
       "bounds": [2008, 2008],
       "contentsOpaque": true,
-      "backgroundColor": "#FFFFFF"
+      "backgroundColor": "#0000FF"
     }
   ]
 }
@@ -34,7 +34,7 @@
       "name": "Scrolling Contents Layer",
       "bounds": [2008, 2008],
       "contentsOpaque": true,
-      "backgroundColor": "#FFFFFF"
+      "backgroundColor": "#0000FF"
     }
   ]
 }

third_party/blink/web_tests/platform/linux/paint/invalidation/selection/selection-within-composited-scroller-expected.txt

@@ -33,7 +33,7 @@
       "name": "Scrolling Contents Layer",
       "bounds": [200, 1620],
       "contentsOpaque": true,
-      "backgroundColor": "#D3D3D3",
+      "backgroundColor": "#ADD8E6",
       "invalidations": [
         [0, 610, 22, 20]
       ],

third_party/blink/web_tests/platform/mac-mac10.13/paint/invalidation/table/scroll-inside-table-cell-expected.txt

@@ -4,7 +4,7 @@
       "name": "Scrolling Contents Layer",
       "bounds": [800, 600],
       "contentsOpaque": true,
-      "backgroundColor": "#FFFFFF",
+      "backgroundColor": "#FF0000",
       "invalidations": [
         [314, 114, 435, 450],
         [314, 564, 435, 15]

third_party/blink/web_tests/platform/mac/paint/invalidation/selection/selection-within-composited-scroller-expected.txt

@@ -33,7 +33,7 @@
       "name": "Scrolling Contents Layer",
       "bounds": [200, 1620],
       "contentsOpaque": true,
-      "backgroundColor": "#D3D3D3",
+      "backgroundColor": "#ADD8E6",
       "invalidations": [
         [0, 610, 23, 18]
       ],

third_party/blink/web_tests/platform/mac/paint/invalidation/table/scroll-inside-table-cell-expected.txt

@@ -4,7 +4,7 @@
       "name": "Scrolling Contents Layer",
       "bounds": [800, 600],
       "contentsOpaque": true,
-      "backgroundColor": "#FFFFFF"
+      "backgroundColor": "#FF0000"
     },
     {
       "name": "LayoutNGTableCell (relative positioned) TD id='cellToScroll' class='relative'",

third_party/blink/web_tests/platform/win/paint/invalidation/selection/selection-within-composited-scroller-expected.txt

@@ -33,7 +33,7 @@
       "name": "Scrolling Contents Layer",
       "bounds": [200, 1620],
       "contentsOpaque": true,
-      "backgroundColor": "#D3D3D3",
+      "backgroundColor": "#ADD8E6",
       "invalidations": [
         [0, 610, 21, 20]
       ],

third_party/blink/web_tests/paint/invalidation/table/scroll-inside-table-cell-expected.txt → third_party/blink/web_tests/platform/win/paint/invalidation/table/scroll-inside-table-cell-expected.txt

@@ -4,7 +4,7 @@
       "name": "Scrolling Contents Layer",
       "bounds": [800, 600],
       "contentsOpaque": true,
-      "backgroundColor": "#FFFFFF",
+      "backgroundColor": "#FF0000",
       "invalidations": [
         [314, 114, 435, 450],
         [314, 564, 435, 15]