Audit the use of updateStyleAndLayoutIgnorePendingStylesheets in canonicalPosition

third_party/WebKit/Source/core/editing/VisibleUnits.cpp

 /*
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 84 matching lines @@
     // FIXME (9535):  Canonicalizing to the leftmost candidate means that if
     // we're at a line wrap, we will ask layoutObjects to paint downstream
     // carets for other layoutObjects. To fix this, we need to either a) add
     // code to all paintCarets to pass the responsibility off to the appropriate
     // layoutObject for VisiblePosition's like these, or b) canonicalize to the
     // rightmost candidate unless the affinity is upstream.
     if (position.isNull())
         return PositionType();
 
     DCHECK(position.document());
-    position.document()->updateStyleAndLayoutIgnorePendingStylesheets();
+    DCHECK(!position.document()->needsLayoutTreeUpdate());
 
     Node* node = position.computeContainerNode();
 
     PositionType candidate = mostBackwardCaretPosition(position);
     if (isVisuallyEquivalentCandidate(candidate))
         return candidate;
     candidate = mostForwardCaretPosition(position);
     if (isVisuallyEquivalentCandidate(candidate))
         return candidate;
 
@@ skipping 1117 matching lines @@
 VisiblePositionInFlatTree logicalEndOfLine(const VisiblePositionInFlatTree& currentPosition)
 {
     return logicalEndOfLineAlgorithm<EditingInFlatTreeStrategy>(currentPosition);
 }
 
 template <typename Strategy>
 bool inSameLineAlgorithm(const PositionWithAffinityTemplate<Strategy>& position1, const PositionWithAffinityTemplate<Strategy>& position2)
 {
     if (position1.isNull() || position2.isNull())
         return false;
+    if (position1.position().document() != position2.position().document())

[yosin_UTC9, 2016/09/12 09:25:03]

Could you change this to DCHEC_EQ(position1.position().document(),
position2.position().document())?

[Xiaocheng, 2016/09/12 11:20:49]

Done.

Haven't found any call site that may compare two positions in different
documents. And it's also weird if there is any.

+        return false;
+
+    // TODO(xiaochengh): The use of updateStyleAndLayoutIgnorePendingStylesheets
+    // needs to be audited.  See http://crbug.com/590369 for more details.
+    position1.position().document()->updateStyleAndLayoutIgnorePendingStylesheets();
+
     PositionWithAffinityTemplate<Strategy> startOfLine1 = startOfLine(position1);
     PositionWithAffinityTemplate<Strategy> startOfLine2 = startOfLine(position2);
     if (startOfLine1 == startOfLine2)
         return true;
     PositionTemplate<Strategy> canonicalized1 = canonicalPositionOf(startOfLine1.position());
     if (canonicalized1 == startOfLine2.position())
         return true;
     return canonicalized1 == canonicalPositionOf(startOfLine2.position());
 }
 
@@ skipping 2063 matching lines @@
 {
     return previousPositionOfAlgorithm<EditingStrategy>(visiblePosition, rule);
 }
 
 VisiblePositionInFlatTree previousPositionOf(const VisiblePositionInFlatTree& visiblePosition, EditingBoundaryCrossingRule rule)
 {
     return previousPositionOfAlgorithm<EditingInFlatTreeStrategy>(visiblePosition, rule);
 }
 
 } // namespace blink