[Line Layout API] Use LineLayoutItem consistently in RootInlineBox::childRemoved

The class has m_lineBreakObj, which has already been converted to the new API.
This CL updates the childRemoved method to use box->lineLayoutItem() for
comparisons to m_lineBreakObj and for iterating.

BUG=499321

Review URL: https://codereview.chromium.org/1296803004

git-svn-id: svn://svn.chromium.org/blink/trunk@200841 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/Source/core/layout/line/RootInlineBox.cpp

@@ -182,10 +182,10 @@ void RootInlineBox::move(const LayoutSize& delta)
 
 void RootInlineBox::childRemoved(InlineBox* box)
 {
-    if (&box->layoutObject() == m_lineBreakObj)
+    if (box->lineLayoutItem() == m_lineBreakObj)
         setLineBreakInfo(0, 0, BidiStatus());
 
-    for (RootInlineBox* prev = prevRootBox(); prev && prev->lineBreakObj() == &box->layoutObject(); prev = prev->prevRootBox()) {
+    for (RootInlineBox* prev = prevRootBox(); prev && prev->lineBreakObj() == box->lineLayoutItem(); prev = prev->prevRootBox()) {
         prev->setLineBreakInfo(0, 0, BidiStatus());
         prev->markDirty();
     }