Make InlineBoxPosition constructor not to accept null-InlineBox

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

 /*
  * Copyright (C) 2004 Apple Computer, 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 34 matching lines @@
 
 enum EWordSide { kRightWordIfOnBoundary = false, kLeftWordIfOnBoundary = true };
 
 struct InlineBoxPosition {
   InlineBox* inline_box;
   int offset_in_box;
 
   InlineBoxPosition() : inline_box(nullptr), offset_in_box(0) {}
 
   InlineBoxPosition(InlineBox* inline_box, int offset_in_box)
-      : inline_box(inline_box), offset_in_box(offset_in_box) {}
+      : inline_box(inline_box), offset_in_box(offset_in_box) {
+    DCHECK(inline_box);
+    DCHECK_GE(offset_in_box, 0);
+  }
 
   bool operator==(const InlineBoxPosition& other) const {
     return inline_box == other.inline_box &&
            offset_in_box == other.offset_in_box;
   }
 
   bool operator!=(const InlineBoxPosition& other) const {
     return !operator==(other);
   }
 };
@@ skipping 317 matching lines @@
                                             const VisiblePosition&,
                                             EditableType);
 
 Position PreviousRootInlineBoxCandidatePosition(Node*,
                                                 const VisiblePosition&,
                                                 EditableType);
 
 }  // namespace blink
 
 #endif  // VisibleUnits_h