Force adding sheets and recalc for html import re-ordering.

third_party/WebKit/Source/core/css/ActiveStyleSheetsTest.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/css/ActiveStyleSheets.h"
 
 #include "core/css/CSSStyleSheet.h"
 #include "core/css/MediaQueryEvaluator.h"
 #include "core/css/StyleSheetContents.h"
 #include "core/css/StyleSheetList.h"
@@ skipping 284 matching lines @@
 
   newSheets.append(std::make_pair(sheet1, &sheet1->contents()->ruleSet()));
   newSheets.append(std::make_pair(sheet3, &sheet3->contents()->ruleSet()));
 
   EXPECT_EQ(ActiveSheetsChanged,
             compareActiveStyleSheets(oldSheets, newSheets, changedRuleSets));
   ASSERT_EQ(1u, changedRuleSets.size());
   EXPECT_EQ(&sheet3->contents()->ruleSet(), changedRuleSets[0]);
 }
 
+TEST_F(ActiveStyleSheetsTest, CompareActiveStyleSheets_ReorderedImportSheets) {
+  ActiveStyleSheetVector oldSheets;
+  ActiveStyleSheetVector newSheets;
+  HeapVector<Member<RuleSet>> changedRuleSets;
+
+  CSSStyleSheet* sheet1 = createSheet();
+  CSSStyleSheet* sheet2 = createSheet();
+
+  // It is possible to have CSSStyleSheet pointers re-orderered for html imports
+  // because their documents, and hence their stylesheets are persisted on
+  // remove / insert. This test is here to show that the active sheet comparison
+  // is not able to see that anything changed.
+  //
+  // Imports are handled by forcing re-append and recalc of the document scope
+  // when html imports are removed.
+  oldSheets.append(std::make_pair(sheet1, &sheet1->contents()->ruleSet()));
+  oldSheets.append(std::make_pair(sheet2, &sheet2->contents()->ruleSet()));
+
+  newSheets.append(std::make_pair(sheet2, &sheet2->contents()->ruleSet()));
+  newSheets.append(std::make_pair(sheet1, &sheet1->contents()->ruleSet()));
+
+  EXPECT_EQ(NoActiveSheetsChanged,
+            compareActiveStyleSheets(oldSheets, newSheets, changedRuleSets));
+  EXPECT_EQ(0u, changedRuleSets.size());
+}
+
 TEST_F(ApplyRulesetsTest, AddUniversalRuleToDocument) {
   document().view()->updateAllLifecyclePhases();
 
   CSSStyleSheet* sheet = createSheet("body * { color:red }");
 
   ActiveStyleSheetVector newStyleSheets;
   newStyleSheets.append(std::make_pair(sheet, &sheet->contents()->ruleSet()));
 
   styleEngine().applyRuleSetChanges(document(), ActiveStyleSheetVector(),
                                     newStyleSheets);
@@ skipping 110 matching lines @@
   ActiveStyleSheetVector oldStyleSheets;
   oldStyleSheets.append(
       std::make_pair(cssSheet, &cssSheet->contents()->ruleSet()));
   styleEngine().applyRuleSetChanges(shadowRoot, oldStyleSheets,
                                     ActiveStyleSheetVector());
 
   EXPECT_TRUE(styleEngine().treeBoundaryCrossingScopes().isEmpty());
 }
 
 }  // namespace blink