Make leadingWhitespacePosition() to respect "white-space" CSS property

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

Index: third_party/WebKit/Source/core/editing/EditingUtilities.h
diff --git a/third_party/WebKit/Source/core/editing/EditingUtilities.h b/third_party/WebKit/Source/core/editing/EditingUtilities.h
index 7632c5c301dd84e422655ae272cb36b297805770..8e38eff6833481bf87f9a9b783bbfdc7ec7fb01c 100644
--- a/third_party/WebKit/Source/core/editing/EditingUtilities.h
+++ b/third_party/WebKit/Source/core/editing/EditingUtilities.h
@@ -241,6 +241,14 @@ bool isAtUnsplittableElement(const Position&);
 // miscellaneous functions on Position
 
 enum WhitespacePositionOption { NotConsiderNonCollapsibleWhitespace, ConsiderNonCollapsibleWhitespace };
+
+// |leadingWhitespacePosition(position)| returns a previous position of
+// |position| if it is at collapsible whitespace, otherwise it returns null
+// position. When it is called with |NotConsiderNonCollapsibleWhitespace| and
+// a previous position in a element which has CSS property "white-space:pre",
+// or its variant, |leadingWhitespacePosition()| returns null position.
+// TODO(yosin) We should rename |leadingWhitespacePosition()| to
+// |leadingCollapsibleWhitespacePosition()| as this function really returns.
 Position leadingWhitespacePosition(const Position&, TextAffinity, WhitespacePositionOption = NotConsiderNonCollapsibleWhitespace);
 Position trailingWhitespacePosition(const Position&, TextAffinity, WhitespacePositionOption = NotConsiderNonCollapsibleWhitespace);
 unsigned numEnclosingMailBlockquotes(const Position&);