[BlinkGenPropertyTrees] Collect non-drawing layers for hit testing

Some non-drawing layers need to be collected for hit testing. For example, if there's a composited animation on an empty div, we still need to create a composited layer for the purposes of hit testing. Bug: 870728 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: Ibbf8bcd60242b901db9b35821450111d4a7c5d63 Reviewed-on: https://chromium-review.googlesource.com/1180464Reviewed-by: Tien-Ren Chen <trchen@chromium.org> Commit-Queue: Philip Rogers <pdr@chromium.org> Cr-Commit-Position: refs/heads/master@{#584267}

[BlinkGenPropertyTrees] Collect non-drawing layers for hit testing
Some non-drawing layers need to be collected for hit testing. For example, if there's a composited animation on an empty div, we still need to create a composited layer for the purposes of hit testing. Bug: 870728 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: Ibbf8bcd60242b901db9b35821450111d4a7c5d63 Reviewed-on: https://chromium-review.googlesource.com/1180464Reviewed-by: Tien-Ren Chen <trchen@chromium.org> Commit-Queue: Philip Rogers <pdr@chromium.org> Cr-Commit-Position: refs/heads/master@{#584267}
c1637af7 · Philip Rogers · Commit Bot · eb0a66c4 · c1637af7 · c1637af7
Commit c1637af7 authored Aug 18, 2018 by Philip Rogers Committed by Commit Bot Aug 18, 2018
5 changed files
--- a/third_party/WebKit/LayoutTests/virtual/threaded/animations/invisible-composited-animations-prevent-scroll-expected.html
+++ b/third_party/WebKit/LayoutTests/virtual/threaded/animations/invisible-composited-animations-prevent-scroll-expected.html
+<!doctype html>
+<style>
+.scroll {
+  overflow: auto;
+  width: 100px;
+  height: 100px;
+  will-change: transform;
+}
+.scrolled-content {
+  width: 50px;
+  height: 1000px;
+  background-image: linear-gradient(green, red);
+}
+</style>
+It should not be possible to scroll this content:<br>
+<div class="scroll">
+  <div class="scrolled-content"></div>
+</div>
--- a/third_party/WebKit/LayoutTests/virtual/threaded/animations/invisible-composited-animations-prevent-scroll.html
+++ b/third_party/WebKit/LayoutTests/virtual/threaded/animations/invisible-composited-animations-prevent-scroll.html
+<!doctype html>
+<style>
+.scroll {
+  overflow: auto;
+  width: 100px;
+  height: 100px;
+  will-change: transform;
+}
+.scrolled-content {
+  width: 50px;
+  height: 1000px;
+  background-image: linear-gradient(green, red);
+}
+#animated-overlap {
+  height: 100px;
+  width: 110px;
+  animation: cover 1s infinite;
+}
+@keyframes cover {
+  0% { transform: translateY(0); }
+  1% { transform: translateY(-100px); }
+  100% { transform: translateY(-100px); }
+}
+</style>
+It should not be possible to scroll this content:<br>
+<div class="scroll">
+  <div class="scrolled-content"></div>
+</div>
+<div id="animated-overlap"></div>
+<script>
+  testRunner.waitUntilDone();
+  // Wait for the animation to advance.
+  requestAnimationFrame(function() {
+    const GESTURE_SOURCE_TYPE = 2; // MOUSE_INPUT from synthetic_gesture_params.h
+      chrome.gpuBenchmarking.smoothScrollBy(
+        1000,
+        function() {
+          testRunner.notifyDone();
+        },
+        50 /* start_x */,
+        50 /* start_y */,
+        GESTURE_SOURCE_TYPE,
+        'down',
+        20000 /* speed */);
+  });
+</script>
--- a/third_party/blink/renderer/core/frame/local_frame_view.cc
+++ b/third_party/blink/renderer/core/frame/local_frame_view.cc
@@ -2708,7 +2708,11 @@ static void CollectDrawableLayersForLayerListRecursively(
  if (!layer || layer->Client().ShouldThrottleRendering())
    return;
-  if (layer->DrawsContent()) {
+  // We need to collect all layers that draw content, as well as some layers
+  // that don't for the purposes of hit testing. For example, an empty div
+  // will not draw content but needs to create a layer to ensure scroll events
+  // do not pass through it.
+  if (layer->DrawsContent() || layer->GetHitTestableWithoutDrawsContent()) {
    ScopedPaintChunkProperties scope(context.GetPaintController(),
                                     layer->GetPropertyTreeState(), *layer,
                                     DisplayItem::kForeignLayerWrapper);

--- a/third_party/blink/renderer/core/paint/compositing/composited_layer_mapping_test.cc
+++ b/third_party/blink/renderer/core/paint/compositing/composited_layer_mapping_test.cc
@@ -1038,8 +1038,7 @@ TEST_F(CompositedLayerMappingTest,
      mapping->ForegroundLayer()->PaintingPhase());
  // Regression test for crbug.com/767908: a foreground layer should also
  // participates hit testing.
-  EXPECT_TRUE(mapping->ForegroundLayer()
+  EXPECT_TRUE(mapping->ForegroundLayer()->GetHitTestableWithoutDrawsContent());
-                  ->GetHitTestableWithoutDrawsContentForTesting());
  Element* negative_composited_child =
      GetDocument().getElementById("negative-composited-child");

--- a/third_party/blink/renderer/platform/graphics/graphics_layer.h
+++ b/third_party/blink/renderer/platform/graphics/graphics_layer.h
@@ -188,7 +188,7 @@ class PLATFORM_EXPORT GraphicsLayer : public cc::LayerClient,
  void SetIsRootForIsolatedGroup(bool);
  void SetHitTestableWithoutDrawsContent(bool);
-  bool GetHitTestableWithoutDrawsContentForTesting() {
+  bool GetHitTestableWithoutDrawsContent() const {
    return hit_testable_without_draws_content_;
  }