Change ContentData::operator== to iterate through whole list.

third_party/WebKit/Source/core/style/ContentData.h

Index: third_party/WebKit/Source/core/style/ContentData.h
diff --git a/third_party/WebKit/Source/core/style/ContentData.h b/third_party/WebKit/Source/core/style/ContentData.h
index b7a1df0bdb9364a1af5ef39b7433d86970cc4f0e..7d4b842777fa9658c6e275f877fc8a7bd3549008 100644
--- a/third_party/WebKit/Source/core/style/ContentData.h
+++ b/third_party/WebKit/Source/core/style/ContentData.h
@@ -200,11 +200,15 @@ class QuoteContentData final : public ContentData {
 DEFINE_CONTENT_DATA_TYPE_CASTS(Quote);
 
 inline bool operator==(const ContentData& a, const ContentData& b) {
-  return a.Equals(b);
-}
+  const ContentData* ptr_a = &a;
+  const ContentData* ptr_b = &b;
+
+  while (ptr_a && ptr_b && ptr_a->Equals(*ptr_b)) {
+    ptr_a = ptr_a->Next();
+    ptr_b = ptr_b->Next();
+  }
 
-inline bool operator!=(const ContentData& a, const ContentData& b) {
-  return !(a == b);
+  return !ptr_a && !ptr_b;
 }
 
 }  // namespace blink