Add position sticky main thread scrolling reason [spv2]

third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilderTest.cpp

Index: third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilderTest.cpp
diff --git a/third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilderTest.cpp b/third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilderTest.cpp
index 8df7d78641100b05b9b99f573e86aeb42f1a9abb..51228b41255cb0217c72fb62e504a01995a1a456 100644
--- a/third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilderTest.cpp
+++ b/third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilderTest.cpp
@@ -2009,7 +2009,7 @@ TEST_P(PaintPropertyTreeBuilderTest, SVGRootNoClip)
     EXPECT_FALSE(getLayoutObjectByElementId("svg")->objectPaintProperties()->overflowClip());
 }
 
-TEST_P(PaintPropertyTreeBuilderTest, MainThreadScrollReasonsWithNestedScrollers)
+TEST_P(PaintPropertyTreeBuilderTest, BackgroundAttachmentFixedMainThreadScrollReasonsWithNestedScrollers)
 {
     setBodyInnerHTML(
         "<style>"
@@ -2062,7 +2062,7 @@ TEST_P(PaintPropertyTreeBuilderTest, MainThreadScrollReasonsWithNestedScrollers)
     EXPECT_FALSE(overflowB->layoutObject()->objectPaintProperties()->scroll()->hasMainThreadScrollingReasons(MainThreadScrollingReason::kHasBackgroundAttachmentFixedObjects));
 }
 
-TEST_P(PaintPropertyTreeBuilderTest, MainThreadScrollReasonsWithFixedScroller)
+TEST_P(PaintPropertyTreeBuilderTest, BackgroundAttachmentFixedMainThreadScrollReasonsWithFixedScroller)
 {
     setBodyInnerHTML(
         "<style>"
@@ -2108,4 +2108,56 @@ TEST_P(PaintPropertyTreeBuilderTest, MainThreadScrollReasonsWithFixedScroller)
     EXPECT_FALSE(overflowB->layoutObject()->objectPaintProperties()->scroll()->hasMainThreadScrollingReasons(MainThreadScrollingReason::kHasBackgroundAttachmentFixedObjects));
 }
 
+TEST_P(PaintPropertyTreeBuilderTest, PositionStickyMainThreadScrollReasonsWithNestedScrollers)
+{
+    setBodyInnerHTML(
+        "<style>"
+        "  #overflowA {"
+        "    overflow: scroll;"
+        "    width: 20px;"
+        "    height: 20px;"
+        "  }"
+        "  #overflowB {"
+        "    overflow: scroll;"
+        "    width: 5px;"
+        "    height: 3px;"
+        "  }"
+        "  .positionSticky {"
+        "    position: sticky;"
+        "    top: 0;"
+        "    left: 0;"
+        "  }"
+        "  .forceScroll {"
+        "    height: 4000px;"
+        "  }"
+        "</style>"
+        "<div id='overflowA'>"
+        "  <div id='overflowB' class='positionSticky'>"

[chrishtr, 2016/09/20 19:45:57]

It's a little weird that you put position:sticky on the scroll itself. Child
instead?

[pdr., 2016/09/20 20:16:57]

It is weird and I doubt anyone will do it, but I think it's important to test
the case where the scroller itself is sticky. This same issue took me a while to
work through and explain for background attachment fixed
(https://codereview.chromium.org/2345403003#msg6), and this test is the same
except for sticky. The tldr version is: when we declare something as sticky,
it's scrolled contents are not necessarily sticky but it's parent scroll node is
sticky. This is why we expect_false that overflow b's scroll node has sticky
positioned objects (line 2146), even though overflow b itself is sticky.

Here's real example of the situation: http://output.jsbin.com/foheli
(requires --enable-experimental-web-platform-features since sticky has not
shipped)

[chrishtr, 2016/09/20 20:29:35]

Ok makes sense. Please also add a test for an element within the scroller.

+        "    <div class='forceScroll'></div>"
+        "  </div>"
+        "  <div class='forceScroll'></div>"
+        "</div>"
+        "<div class='forceScroll'></div>");
+    Element* overflowA = document().getElementById("overflowA");
+    Element* overflowB = document().getElementById("overflowB");
+
+    EXPECT_TRUE(frameScroll()->hasMainThreadScrollingReasons(MainThreadScrollingReason::kHasStickyPositionObjects));
+    EXPECT_TRUE(overflowA->layoutObject()->objectPaintProperties()->scroll()->hasMainThreadScrollingReasons(MainThreadScrollingReason::kHasStickyPositionObjects));
+    EXPECT_FALSE(overflowB->layoutObject()->objectPaintProperties()->scroll()->hasMainThreadScrollingReasons(MainThreadScrollingReason::kHasStickyPositionObjects));
+
+    // Removing a main thread scrolling reason should update the entire tree.
+    overflowB->removeAttribute("class");
+    document().view()->updateAllLifecyclePhases();
+    EXPECT_FALSE(frameScroll()->hasMainThreadScrollingReasons(MainThreadScrollingReason::kHasStickyPositionObjects));
+    EXPECT_FALSE(overflowA->layoutObject()->objectPaintProperties()->scroll()->hasMainThreadScrollingReasons(MainThreadScrollingReason::kHasStickyPositionObjects));
+    EXPECT_FALSE(overflowB->layoutObject()->objectPaintProperties()->scroll()->hasMainThreadScrollingReasons(MainThreadScrollingReason::kHasStickyPositionObjects));
+
+    // Adding a main thread scrolling reason should update the entire tree.
+    overflowB->setAttribute(HTMLNames::classAttr, "positionSticky");
+    document().view()->updateAllLifecyclePhases();
+    EXPECT_TRUE(frameScroll()->hasMainThreadScrollingReasons(MainThreadScrollingReason::kHasStickyPositionObjects));
+    EXPECT_TRUE(overflowA->layoutObject()->objectPaintProperties()->scroll()->hasMainThreadScrollingReasons(MainThreadScrollingReason::kHasStickyPositionObjects));
+    EXPECT_FALSE(overflowB->layoutObject()->objectPaintProperties()->scroll()->hasMainThreadScrollingReasons(MainThreadScrollingReason::kHasStickyPositionObjects));
+}
+
 } // namespace blink