Return ActiveSheetsChanged when rulesets change in common prefix.

third_party/WebKit/Source/core/css/ActiveStyleSheets.cpp

Index: third_party/WebKit/Source/core/css/ActiveStyleSheets.cpp
diff --git a/third_party/WebKit/Source/core/css/ActiveStyleSheets.cpp b/third_party/WebKit/Source/core/css/ActiveStyleSheets.cpp
index cca65e7a1cc18a19e12f776f23d716ee70dfc917..47f411dfc765e73a47c729ff23522845a727781e 100644
--- a/third_party/WebKit/Source/core/css/ActiveStyleSheets.cpp
+++ b/third_party/WebKit/Source/core/css/ActiveStyleSheets.cpp
@@ -38,18 +38,15 @@ ActiveSheetsChange compareActiveStyleSheets(
   }
 
   if (index == oldStyleSheetCount) {
-    if (index == newStyleSheetCount) {
-      return changedRuleSets.isEmpty() ? NoActiveSheetsChanged
-                                       : ActiveSheetsChanged;
-    }
-
-    // Sheets added at the end.
+    ActiveSheetsChange change =
+        changedRuleSets.isEmpty() ? NoActiveSheetsChanged : ActiveSheetsChanged;
     for (; index < newStyleSheetCount; index++) {
       if (newStyleSheets[index].second)
         changedRuleSets.add(newStyleSheets[index].second);
     }
-    return changedRuleSets.isEmpty() ? NoActiveSheetsChanged
-                                     : ActiveSheetsAppended;
+    if (change == NoActiveSheetsChanged && !changedRuleSets.isEmpty())
+      change = ActiveSheetsAppended;
+    return change;

[sashab, 2017/01/23 22:06:33]

I'm having trouble comparing these two logic. So the old logic was:

if (index == newStyleSheetCount && changedRuleSets.isEmpty()) ->
NoActiveSheetsChanged
if (index == newStyleSheetCount && !changedRuleSets.isEmpty()) ->
ActiveSheetsChanged
...
if (changedRuleSets.isEmpty()) -> NoActiveSheetsChanged
if (changedRuleSets.isEmpty()) -> ActiveSheetsAppended

New logic:

if (oldchangedRuleSets.isEmpty() && !changedRuleSets.isEmpty()) ->
ActiveSheetsAppended
if (!oldchangedRuleSets.isEmpty() && !changedRuleSets.isEmpty()) ->
ActiveSheetsChanged

This can probably be written in a simpler way, without the ActiveSheetsChange
enum ternary but just bool noChangedRuleSets = !changedRuleSets.isEmpty(). And
then just a ternary operator/if-return at the end.

[rune, 2017/01/24 01:08:10]

Tried with a bool approach now.

   }
 
   if (index == newStyleSheetCount) {