diff --git a/dom/base/nsLineBreaker.cpp b/dom/base/nsLineBreaker.cpp
index 39041f221a977..46a644588ff91 100644
--- a/dom/base/nsLineBreaker.cpp
+++ b/dom/base/nsLineBreaker.cpp
@@ -282,274 +282,6 @@ intl
 :
 WordBreakRule
 ;
-/
-/
-There
-is
-no
-break
-opportunity
-between
-any
-pair
-of
-characters
-that
-has
-line
-/
-/
-break
-class
-of
-either
-AL
-(
-Alphabetic
-)
-IS
-(
-Infix
-Numeric
-Separator
-)
-NU
-/
-/
-(
-Numeric
-)
-or
-QU
-(
-Quotation
-)
-.
-See
-/
-/
-https
-:
-/
-/
-www
-.
-unicode
-.
-org
-/
-Public
-/
-UCD
-/
-latest
-/
-ucd
-/
-LineBreak
-.
-txt
-for
-Unicode
-code
-/
-/
-point
-and
-line
-break
-class
-mapping
-.
-static
-constexpr
-uint8_t
-kNonBreakableASCII
-[
-]
-=
-{
-/
-/
-clang
--
-format
-off
-/
-/
-0x20
--
-0x2f
-0
-0
-1
-1
-0
-0
-1
-1
-0
-0
-1
-0
-1
-0
-1
-0
-/
-/
-0x30
--
-0x3f
-1
-1
-1
-1
-1
-1
-1
-1
-1
-1
-1
-1
-1
-1
-1
-0
-/
-/
-0x40
--
-0x4f
-1
-1
-1
-1
-1
-1
-1
-1
-1
-1
-1
-1
-1
-1
-1
-1
-/
-/
-0x50
--
-0x5f
-1
-1
-1
-1
-1
-1
-1
-1
-1
-1
-1
-0
-0
-0
-1
-1
-/
-/
-0x60
--
-0x6f
-1
-1
-1
-1
-1
-1
-1
-1
-1
-1
-1
-1
-1
-1
-1
-1
-/
-/
-0x70
--
-0x7f
-1
-1
-1
-1
-1
-1
-1
-1
-1
-1
-1
-0
-0
-0
-1
-0
-/
-/
-clang
--
-format
-on
-}
-;
-template
-<
-typename
-T
->
-static
-constexpr
-bool
-IsNonBreakableChar
-(
-T
-aChar
-)
-{
-if
-(
-aChar
-<
-0x20
-|
-|
-aChar
->
-0x7f
-)
-{
-return
-false
-;
-}
-return
-!
-!
-kNonBreakableASCII
-[
-aChar
--
-0x20
-]
-;
-}
 nsLineBreaker
 :
 :
@@ -565,6 +297,10 @@ mCurrentWordContainsMixedLang
 (
 false
 )
+mCurrentWordContainsComplexChar
+(
+false
+)
 mScriptIsChineseOrJapanese
 (
 false
@@ -1137,7 +873,7 @@ else
 if
 (
 !
-mCurrentWordMightBeBreakable
+mCurrentWordContainsComplexChar
 )
 {
 /
@@ -1710,7 +1446,7 @@ Clear
 (
 )
 ;
-mCurrentWordMightBeBreakable
+mCurrentWordContainsComplexChar
 =
 false
 ;
@@ -1882,14 +1618,10 @@ offset
 if
 (
 !
-mCurrentWordMightBeBreakable
+mCurrentWordContainsComplexChar
 &
 &
-!
-IsNonBreakableChar
-<
-char16_t
->
+IsComplexChar
 (
 aText
 [
@@ -1898,7 +1630,7 @@ offset
 )
 )
 {
-mCurrentWordMightBeBreakable
+mCurrentWordContainsComplexChar
 =
 true
 ;
@@ -2221,7 +1953,7 @@ wordStart
 offset
 ;
 bool
-wordMightBeBreakable
+wordHasComplexChar
 =
 false
 ;
@@ -2440,7 +2172,7 @@ wordStart
 else
 if
 (
-wordMightBeBreakable
+wordHasComplexChar
 )
 {
 /
@@ -2555,7 +2287,7 @@ wordStart
 ;
 }
 }
-wordMightBeBreakable
+wordHasComplexChar
 =
 false
 ;
@@ -2582,26 +2314,22 @@ wordStart
 =
 offset
 ;
-continue
-;
 }
+else
+{
 if
 (
 !
-wordMightBeBreakable
+wordHasComplexChar
 &
 &
-!
-IsNonBreakableChar
-<
-char16_t
->
+IsComplexChar
 (
 ch
 )
 )
 {
-wordMightBeBreakable
+wordHasComplexChar
 =
 true
 ;
@@ -2623,9 +2351,9 @@ aLength
 Save
 this
 word
-mCurrentWordMightBeBreakable
+mCurrentWordContainsComplexChar
 =
-wordMightBeBreakable
+wordHasComplexChar
 ;
 uint32_t
 len
@@ -2643,10 +2371,6 @@ mCurrentWord
 AppendElements
 (
 len
-mozilla
-:
-:
-fallible
 )
 ;
 if
@@ -2715,6 +2439,7 @@ break
 ;
 }
 }
+}
 if
 (
 aSink
@@ -3050,14 +2775,10 @@ offset
 if
 (
 !
-mCurrentWordMightBeBreakable
+mCurrentWordContainsComplexChar
 &
 &
-!
-IsNonBreakableChar
-<
-uint8_t
->
+IsComplexASCIIChar
 (
 aText
 [
@@ -3066,7 +2787,7 @@ offset
 )
 )
 {
-mCurrentWordMightBeBreakable
+mCurrentWordContainsComplexChar
 =
 true
 ;
@@ -3320,7 +3041,7 @@ wordStart
 offset
 ;
 bool
-wordMightBeBreakable
+wordHasComplexChar
 =
 false
 ;
@@ -3514,7 +3235,7 @@ wordStart
 else
 if
 (
-wordMightBeBreakable
+wordHasComplexChar
 )
 {
 /
@@ -3576,7 +3297,7 @@ wordStart
 ;
 }
 }
-wordMightBeBreakable
+wordHasComplexChar
 =
 false
 ;
@@ -3603,26 +3324,22 @@ wordStart
 =
 offset
 ;
-continue
-;
 }
+else
+{
 if
 (
 !
-wordMightBeBreakable
+wordHasComplexChar
 &
 &
-!
-IsNonBreakableChar
-<
-uint8_t
->
+IsComplexASCIIChar
 (
 ch
 )
 )
 {
-wordMightBeBreakable
+wordHasComplexChar
 =
 true
 ;
@@ -3644,9 +3361,9 @@ aLength
 Save
 this
 word
-mCurrentWordMightBeBreakable
+mCurrentWordContainsComplexChar
 =
-wordMightBeBreakable
+wordHasComplexChar
 ;
 uint32_t
 len
@@ -3664,10 +3381,6 @@ mCurrentWord
 AppendElements
 (
 len
-mozilla
-:
-:
-fallible
 )
 ;
 if
@@ -3748,6 +3461,7 @@ break
 ;
 }
 }
+}
 if
 (
 !
diff --git a/dom/base/nsLineBreaker.h b/dom/base/nsLineBreaker.h
index cae56d26d71fb..a237a253be1b5 100644
--- a/dom/base/nsLineBreaker.h
+++ b/dom/base/nsLineBreaker.h
@@ -509,15 +509,22 @@ to
 the
 LineBreaker
 *
+service
 for
 deeper
 analysis
 if
 they
-might
 contain
-breakable
-characters
+a
+"
+complex
+"
+character
+as
+*
+described
+below
 .
 *
 *
@@ -596,6 +603,192 @@ u
 )
 ;
 }
+static
+inline
+bool
+IsComplexASCIIChar
+(
+char16_t
+u
+)
+{
+return
+!
+(
+(
+0x0030
+<
+=
+u
+&
+&
+u
+<
+=
+0x0039
+)
+|
+|
+(
+0x0041
+<
+=
+u
+&
+&
+u
+<
+=
+0x005A
+)
+|
+|
+(
+0x0061
+<
+=
+u
+&
+&
+u
+<
+=
+0x007A
+)
+|
+|
+(
+0x000a
+=
+=
+u
+)
+)
+;
+}
+static
+inline
+bool
+IsComplexChar
+(
+char16_t
+u
+)
+{
+return
+IsComplexASCIIChar
+(
+u
+)
+|
+|
+mozilla
+:
+:
+intl
+:
+:
+NS_NeedsPlatformNativeHandling
+(
+u
+)
+|
+|
+(
+0x1100
+<
+=
+u
+&
+&
+u
+<
+=
+0x11ff
+)
+|
+|
+/
+/
+Hangul
+Jamo
+(
+0x2000
+<
+=
+u
+&
+&
+u
+<
+=
+0x21ff
+)
+|
+|
+/
+/
+Punctuations
+and
+Symbols
+(
+0x2e80
+<
+=
+u
+&
+&
+u
+<
+=
+0xd7ff
+)
+|
+|
+/
+/
+several
+CJK
+blocks
+(
+0xf900
+<
+=
+u
+&
+&
+u
+<
+=
+0xfaff
+)
+|
+|
+/
+/
+CJK
+Compatibility
+Idographs
+(
+0xff00
+<
+=
+u
+&
+&
+u
+<
+=
+0xffef
+)
+;
+/
+/
+Halfwidth
+and
+Fullwidth
+Forms
+}
 /
 /
 Break
@@ -665,12 +858,8 @@ one
 character
 /
 /
-that
-has
-breakable
-line
-breaking
-classes
+matching
+IsComplexChar
 .
 /
 /
@@ -1901,9 +2090,7 @@ bool
 mCurrentWordContainsMixedLang
 ;
 bool
-mCurrentWordMightBeBreakable
-=
-false
+mCurrentWordContainsComplexChar
 ;
 bool
 mScriptIsChineseOrJapanese