Only store previous clip rects for PaintLayers that support subsequences.

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

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/paint/PaintLayer.h"
 
 #include "core/html/HTMLIFrameElement.h"
 #include "core/layout/LayoutBoxModelObject.h"
 #include "core/layout/LayoutTestHelper.h"
 #include "core/layout/LayoutView.h"
@@ skipping 268 matching lines @@
   PaintLayer* parent = GetPaintLayerByElementId("non-stacking-parent");
 
   EXPECT_TRUE(parent->HasNonIsolatedDescendantWithBlendMode());
   EXPECT_TRUE(stacking_parent->HasNonIsolatedDescendantWithBlendMode());
   EXPECT_FALSE(stacking_grandparent->HasNonIsolatedDescendantWithBlendMode());
 
   EXPECT_FALSE(parent->HasDescendantWithClipPath());
   EXPECT_TRUE(parent->HasVisibleDescendant());
 }
 
+TEST_P(PaintLayerTest, SubsequenceCachingStackingContexts) {
+  SetBodyInnerHTML(
+      "<div id='parent' style='position:relative'>"
+      "  <div id='child1' style='position: relative'>"
+      "    <div id='grandchild1' style='position: relative'>"
+      "      <div style='position: relative'></div>"
+      "    </div>"
+      "  </div>"
+      "  <div id='child2' style='isolation: isolate'>"
+      "    <div style='position: relative'></div>"
+      "  </div>"
+      "</div>");
+  PaintLayer* parent = GetPaintLayerByElementId("parent");
+  PaintLayer* child1 = GetPaintLayerByElementId("child1");
+  PaintLayer* child2 = GetPaintLayerByElementId("child2");
+  PaintLayer* grandchild1 = GetPaintLayerByElementId("grandchild1");
+
+  EXPECT_FALSE(parent->SupportsSubsequenceCaching());
+  EXPECT_FALSE(child1->SupportsSubsequenceCaching());
+  EXPECT_TRUE(child2->SupportsSubsequenceCaching());
+  EXPECT_FALSE(grandchild1->SupportsSubsequenceCaching());
+
+  GetDocument()
+      .GetElementById("grandchild1")
+      ->setAttribute(HTMLNames::styleAttr, "isolation: isolate");
+  GetDocument().View()->UpdateAllLifecyclePhases();
+
+  EXPECT_FALSE(parent->SupportsSubsequenceCaching());
+  EXPECT_FALSE(child1->SupportsSubsequenceCaching());
+  EXPECT_TRUE(child2->SupportsSubsequenceCaching());
+  EXPECT_TRUE(grandchild1->SupportsSubsequenceCaching());
+}
+
+TEST_P(PaintLayerTest, SubsequenceCachingSVGRoot) {
+  SetBodyInnerHTML(
+      "<div id='parent' style='position: relative'>"
+      "  <svg id='svgroot' style='position: relative'></svg>"
+      "</div>");
+
+  PaintLayer* svgroot = GetPaintLayerByElementId("svgroot");
+  EXPECT_TRUE(svgroot->SupportsSubsequenceCaching());
+}
+
 TEST_P(PaintLayerTest, HasDescendantWithClipPath) {
   SetBodyInnerHTML(
       "<div id='parent' style='position:relative'>"
       "  <div id='clip-path' style='clip-path: circle(50px at 0 100px)'>"
       "  </div>"
       "</div>");
   PaintLayer* parent = GetPaintLayerByElementId("parent");
   PaintLayer* clip_path = GetPaintLayerByElementId("clip-path");
 
   EXPECT_TRUE(parent->HasDescendantWithClipPath());
@@ skipping 676 matching lines @@
   RefPtr<ComputedStyle> old_style =
       ComputedStyle::Clone(target_object->StyleRef());
   ComputedStyle* new_style = target_object->MutableStyle();
   new_style->SetHasCurrentTransformAnimation();
   target_paint_layer->UpdateTransform(old_style.Get(), *new_style);
 
   EXPECT_NE(nullptr, target_paint_layer->Transform());
 }
 
 }  // namespace blink