Bug 1261265 - Fix nsStyleContext::MoveTo flag assertions to allow mismatch on parents if bit is set on child. r=dholbert

layout/style/nsStyleContext.cpp

@@ -346,17 +346,23 @@ nsStyleContext::MoveTo(nsStyleContext* aNewParent)
   MOZ_ASSERT(aNewParent != mParent);
 
   // This function shouldn't be getting called if the parents have different
-  // values for some flags in mBits, because if that were the case we would need
-  // to recompute those bits for |this|.
-  DebugOnly<uint64_t> mask = NS_STYLE_HAS_PSEUDO_ELEMENT_DATA |
-                             NS_STYLE_IN_DISPLAY_NONE_SUBTREE;
-  MOZ_ASSERT((mParent->mBits & mask) == (aNewParent->mBits & mask));
-  MOZ_ASSERT((mParent->mBits & NS_STYLE_HAS_TEXT_DECORATION_LINES) ==
-             (aNewParent->mBits & NS_STYLE_HAS_TEXT_DECORATION_LINES) ||
-             StyleTextReset()->HasTextDecorationLines());
-  MOZ_ASSERT((mParent->mBits & NS_STYLE_RELEVANT_LINK_VISITED) ==
-             (aNewParent->mBits & NS_STYLE_RELEVANT_LINK_VISITED) ||
-             IsLinkContext());
+  // values for some flags in mBits (unless the flag is also set on this style
+  // context) because if that were the case we would need to recompute those
+  // bits for |this|.
+
+#define CHECK_FLAG(bit_) \
+  MOZ_ASSERT((mParent->mBits & (bit_)) == (aNewParent->mBits & (bit_)) ||     \
+             (mBits & (bit_)),                                                \
+             "MoveTo cannot be called if " #bit_ " value on old and new "     \
+             "style context parents do not match, unless the flag is set "    \
+             "on this style context");
+
+  CHECK_FLAG(NS_STYLE_HAS_PSEUDO_ELEMENT_DATA)
+  CHECK_FLAG(NS_STYLE_IN_DISPLAY_NONE_SUBTREE)
+  CHECK_FLAG(NS_STYLE_HAS_TEXT_DECORATION_LINES)
+  CHECK_FLAG(NS_STYLE_RELEVANT_LINK_VISITED)
+
+#undef CHECK_FLAG
 
   // Assertions checking for visited style are just to avoid some tricky
   // cases we can't be bothered handling at the moment.