Layout tests and unit tests generate different line box trees. We should make them generate the same tree so that layout tests can be converted to unit tests.

Example HTML (repro case grabbed from  crbug.com/752941 ):

<style>
font {
  -webkit-appearance: progress-bar;
}

:first-letter {
  color:black
}

* {
  -webkit-rtl-ordering: visual;
  -webkit-margin-end: -1px
}
</style>
<font dir="rtl">iC <q></q></font>

Layout test generates:

LayoutBlockFlow 0x358371a24250         	FONT
  RootInlineBox 0x358371a300d8         	LayoutBlockFlow 0x358371a24250 {pos=17,0 size=15,19} baseline=15/10
    InlineTextBox 0x358371a64010       	LayoutTextFragment 0x358371a443d0                                         (0,1) "C"
    InlineTextBox 0x358371a64090       	LayoutTextFragment 0x358371a444c0                                         (0,1) "i"
  RootInlineBox 0x358371a301a0         	LayoutBlockFlow 0x358371a24250 {pos=19,20 size=13,19} baseline=15/10
    InlineFlowBox 0x358371a681d8       	LayoutInline 0x358371a40010 {pos=18,20 size=14,19} baseline=15/10
      InlineFlowBox 0x358371a68270     	LayoutInline 0x358371a40180 {pos=18,20 size=7,19} baseline=15/10
        InlineFlowBox 0x358371a68140   	LayoutQuote (anonymous) 0x358371a441f0 {pos=18,20 size=7,19} baseline=15/10
          InlineTextBox 0x358371a64190 	LayoutTextFragment 0x358371a442e0                                         (0,1) """
      InlineFlowBox 0x358371a68010     	LayoutInline 0x358371a400c8 {pos=25,20 size=7,19} baseline=15/10
        InlineFlowBox 0x358371a680a8   	LayoutQuote (anonymous) 0x358371a44010 {pos=25,20 size=7,19} baseline=15/10
          InlineTextBox 0x358371a64110 	LayoutTextFragment 0x358371a44100                                         (0,1) """


Unit test with EditingTestBase generates:

LayoutBlockFlow 0x1d3249e24250         	FONT
  RootInlineBox 0x1d3249e30010         	LayoutBlockFlow 0x1d3249e24250 {pos=1,0 size=0,1} baseline=1/1
    InlineFlowBox 0x1d3249e68140       	LayoutInline 0x1d3249e40010 {pos=0,0 size=0,1} baseline=1/1
      InlineFlowBox 0x1d3249e680a8     	LayoutInline 0x1d3249e40180 {pos=0,0 size=0,1} baseline=1/1
        InlineFlowBox 0x1d3249e68010   	LayoutQuote (anonymous) 0x1d3249e441f0 {pos=0,0 size=0,1} baseline=1/1
          InlineTextBox 0x1d3249e64010 	LayoutTextFragment 0x1d3249e442e0                                         (0,1) """
      InlineFlowBox 0x1d3249e68270     	LayoutInline 0x1d3249e400c8 {pos=0,0 size=0,1} baseline=1/1
        InlineFlowBox 0x1d3249e681d8   	LayoutQuote (anonymous) 0x1d3249e44010 {pos=0,0 size=0,1} baseline=1/1
          InlineTextBox 0x1d3249e64090 	LayoutTextFragment 0x1d3249e44100                                         (0,1) """
    InlineTextBox 0x1d3249e64110       	LayoutTextFragment 0x1d3249e443d0                                         (0,2) "C "
    InlineTextBox 0x1d3249e64190       	LayoutTextFragment 0x1d3249e444c0                                         (0,1) "i"