Don't indent if selection is none.

Source/core/editing/ApplyBlockElementCommand.cpp

 /*
  * Copyright (C) 2006, 2008 Apple Inc. All rights reserved.
  * Copyright (C) 2010 Google 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
@@ skipping 55 matching lines @@
         return;
 
     // When a selection ends at the start of a paragraph, we rarely paint
     // the selection gap before that paragraph, because there often is no gap.
     // In a case like this, it's not obvious to the user that the selection
     // ends "inside" that paragraph, so it would be confusing if Indent/Outdent
     // operated on that paragraph.
     // FIXME: We paint the gap before some paragraphs that are indented with left
     // margin/padding, but not others.  We should make the gap painting more consistent and
     // then use a left margin/padding rule here.
-    if (visibleEnd != visibleStart && isStartOfParagraph(visibleEnd))
+    if (visibleEnd != visibleStart && isStartOfParagraph(visibleEnd)) {
         setEndingSelection(VisibleSelection(visibleStart, visibleEnd.previous(CannotCrossEditingBoundary), endingSelection().isDirectional()));
+        if (endingSelection().isNone())

[Yuta Kitamura, 2014/05/20 09:44:36]

Is this logic equivalent to the following?

    VisibleSelection newSelection(visibleStart,
visibleEnd.previous(CannotCrossEditingBoundary),
endingSelection().isDirectional());
    if (newSelection().isNone())
        return;
    setEndingSelection(newSelection);

If so, I'd say my version is more readable because it exits early,
not after setEndingSelection(). Also there's slight difference in
behavior: with your version, this function ends up clearing
the ending selection which will probably affect subsequent
commands.

[yosin_UTC9, 2014/05/21 03:44:07]

Done.

Yes, you're right. Your version is better than mine.

+            return;
+    }
 
     VisibleSelection selection = selectionForParagraphIteration(endingSelection());
     VisiblePosition startOfSelection = selection.visibleStart();
     VisiblePosition endOfSelection = selection.visibleEnd();
     ASSERT(!startOfSelection.isNull());
     ASSERT(!endOfSelection.isNull());
     RefPtr<ContainerNode> startScope;
     int startIndex = indexForVisiblePosition(startOfSelection, startScope);
     RefPtr<ContainerNode> endScope;
     int endIndex = indexForVisiblePosition(endOfSelection, endScope);
@@ skipping 190 matching lines @@
 
 PassRefPtr<Element> ApplyBlockElementCommand::createBlockElement() const
 {
     RefPtr<Element> element = createHTMLElement(document(), m_tagName);
     if (m_inlineStyle.length())
         element->setAttribute(styleAttr, m_inlineStyle);
     return element.release();
 }
 
 }