Add DCHECK() to check ApplyStyleCommand::DoApply() to work on non-null range

third_party/WebKit/Source/core/editing/commands/ApplyStyleCommand.cpp

 /*
  * Copyright (C) 2005, 2006, 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 181 matching lines @@
 }
 
 Position ApplyStyleCommand::EndPosition() {
   if (use_ending_selection_)
     return EndingSelection().end();
 
   return end_;
 }
 
 void ApplyStyleCommand::DoApply(EditingState* editing_state) {
+  DCHECK(StartPosition().IsNotNull());
+  DCHECK(EndPosition().IsNotNull());
   switch (property_level_) {
     case kPropertyDefault: {
       // Apply the block-centric properties of the style.
       EditingStyle* block_style = style_->ExtractAndRemoveBlockProperties();
       if (!block_style->IsEmpty()) {
         ApplyBlockStyle(block_style, editing_state);
         if (editing_state->IsAborted())
           return;
       }
       // Apply any remaining styles to the inline elements.
@@ skipping 1832 matching lines @@
 
 DEFINE_TRACE(ApplyStyleCommand) {
   visitor->Trace(style_);
   visitor->Trace(start_);
   visitor->Trace(end_);
   visitor->Trace(styled_inline_element_);
   CompositeEditCommand::Trace(visitor);
 }
 
 }  // namespace blink