Fix DCHECK failure when starting an SVG animation

Bug: 1126782
Change-Id: Ib13adc90f6807750e14fbb3ff6a6606f85800eb8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2404154Reviewed-by: Philip Rogers <pdr@chromium.org>
Commit-Queue: Xianzhu Wang <wangxianzhu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#806461}

third_party/blink/renderer/core/layout/layout_object.cc

@@ -2251,7 +2251,8 @@ void LayoutObject::SetStyle(scoped_refptr<const ComputedStyle> style,
       (diff.TransformChanged() || diff.OpacityChanged() ||
        diff.ZIndexChanged() || diff.FilterChanged() ||
        diff.BackdropFilterChanged() || diff.CssClipChanged() ||
-       diff.BlendModeChanged() || diff.MaskChanged())) {
+       diff.BlendModeChanged() || diff.MaskChanged() ||
+       diff.CompositingReasonsChanged())) {
     SetNeedsPaintPropertyUpdate();
   }
 }

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

@@ -1821,4 +1821,24 @@ TEST_P(PaintPropertyTreeUpdateTest, InlineFilterReferenceBoxChange) {
             properties->Filter()->Filter().ReferenceBox().Location());
 }
 
+TEST_P(PaintPropertyTreeUpdateTest, StartSVGAnimation) {
+  SetBodyInnerHTML(R"HTML(
+    <style>line {transition: transform 1s; transform: translateY(1px)}</style>
+    <svg width="200" height="200" stroke="black">
+      <line id="line" x1="0" y1="0" x2="150" y2="50">
+    </svg>
+  )HTML");
+
+  const auto* properties = PaintPropertiesForElement("line");
+  ASSERT_TRUE(properties);
+  ASSERT_TRUE(properties->Transform());
+  EXPECT_FALSE(properties->Transform()->HasDirectCompositingReasons());
+
+  GetDocument().getElementById("line")->setAttribute(
+      html_names::kStyleAttr, "transform: translateY(100px)");
+  UpdateAllLifecyclePhasesForTest();
+  ASSERT_EQ(properties, PaintPropertiesForElement("line"));
+  EXPECT_TRUE(properties->Transform()->HasDirectCompositingReasons());
+}
+
 }  // namespace blink