Fixed word and line navigation in multi-line text fields.

content/browser/accessibility/browser_accessibility.h

Index: content/browser/accessibility/browser_accessibility.h
diff --git a/content/browser/accessibility/browser_accessibility.h b/content/browser/accessibility/browser_accessibility.h
index e0b18bd31f5af2d32dd3bf9401efbf230b562193..4f6b308619dc7983ae7d12d4d111ef9fa1b7dd7c 100644
--- a/content/browser/accessibility/browser_accessibility.h
+++ b/content/browser/accessibility/browser_accessibility.h
@@ -114,6 +114,14 @@ class CONTENT_EXPORT BrowserAccessibility {
 
   // Searches in the given text and from the given offset until the start of
   // the next or previous word is found and returns its position.
+  // In case there is no word boundary before or after the given offset, it
+  // returns one past the last character, i.e. the text's length.
+  // If the given offset is already at the start of a word, returns the start
+  // of the next word if the search is forwards and the given offset if it is
+  // backwards.
+  // If the start offset is equal to -1 and the search is in the forwards
+  // direction, returns the start boundary of the first word.
+  // Start offsets that are not in the range -1 to text length are invalid.
   int GetWordStartBoundary(
       int start, ui::TextBoundaryDirection direction) const;