Fix Japanese line breaking rule before and after ruby

Source/core/layout/LayoutRubyRun.cpp

 /*
  * Copyright (C) 2009 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 284 matching lines @@
     // We overhang a ruby only if the neighboring layout object is a text.
     // We can overhang the ruby by no more than half the width of the neighboring text
     // and no more than half the font size.
     int halfWidthOfFontSize = rubyText->style(firstLine)->fontSize() / 2;
     if (startOverhang)
         startOverhang = std::min<int>(startOverhang, std::min<int>(toLayoutText(startLayoutObject)->minLogicalWidth(), halfWidthOfFontSize));
     if (endOverhang)
         endOverhang = std::min<int>(endOverhang, std::min<int>(toLayoutText(endLayoutObject)->minLogicalWidth(), halfWidthOfFontSize));
 }
 
+bool LayoutRubyRun::canBreakBefore(const LazyLineBreakIterator& iterator) const
+{
+    // TODO(kojii): It would be nice to improve this so that it isn't just
+    // hard-coded, but lookahead in this case is particularly problematic.
+    // See crbug.com/522826.
+
+    if (!iterator.priorContextLength())
+        return true;
+    UChar ch = iterator.lastCharacter();
+    ULineBreak lineBreak = static_cast<ULineBreak>(u_getIntPropertyValue(ch, UCHAR_LINE_BREAK));
+    // UNICODE LINE BREAKING ALGORITHM
+    // http://www.unicode.org/reports/tr14/
+    // And Requirements for Japanese Text Layout, 3.1.7 Characters Not Starting a Line
+    // http://www.w3.org/TR/2012/NOTE-jlreq-20120403/#characters_not_starting_a_line
+    switch (lineBreak) {
+    case U_LB_WORD_JOINER:
+    case U_LB_GLUE:
+    case U_LB_OPEN_PUNCTUATION:
+        return false;
+    default:
+        break;
+    }
+    return true;
+}
+
 } // namespace blink