Switch whitespace mode back to pre-wrap

When we removed position: sticky, we introduced a subtle line breaking
bug to pre-wrap that would cause whitespace to accumulate at the
beginning of lines that follow unclean breaks. This patch adds back the
deleted code (cleansed of the position sticky bits).

sky/engine/core/rendering/line/BreakingContextInlineHeaders.h

@@ -99,6 +99,8 @@ public:
     }
 
 private:
+    void skipTrailingWhitespace(InlineIterator&, const LineInfo&);
+
     InlineBidiResolver& m_resolver;
 
     InlineIterator m_current;
@@ -183,6 +185,18 @@ inline bool requiresLineBox(const InlineIterator& it, const LineInfo& lineInfo =
     return notJustWhitespace || isEmptyInline(it.object());
 }
 
+// FIXME: The entire concept of the skipTrailingWhitespace function is flawed, since we really need to be building
+// line boxes even for containers that may ultimately collapse away. Otherwise we'll never get positioned
+// elements quite right. In other words, we need to build this function's work into the normal line
+// object iteration process.
+// NB. this function will insert any floating elements that would otherwise
+// be skipped but it will not position them.
+inline void BreakingContext::skipTrailingWhitespace(InlineIterator& iterator, const LineInfo& lineInfo)
+{
+    while (!iterator.atEnd() && !requiresLineBox(iterator, lineInfo, TrailingWhitespace))
+        iterator.increment();
+}
+
 inline void BreakingContext::initializeForCurrentObject()
 {
     m_currentStyle = m_current.object()->style();
@@ -551,6 +565,7 @@ inline bool BreakingContext::handleText(WordMeasurements& wordMeasurements, bool
                     if (!m_width.fitsOnLine(charWidth)) {
                         lineWasTooWide = true;
                         m_lineBreak.moveTo(m_current.object(), m_current.offset(), m_current.nextBreakablePosition());
+                        skipTrailingWhitespace(m_lineBreak, m_lineInfo);
                     }
                 }
                 if (lineWasTooWide || !m_width.fitsOnLine()) {

sky/engine/core/rendering/style/RenderStyle.h

@@ -966,7 +966,7 @@ public:
     static EPosition initialPosition() { return StaticPosition; }
     static EUnicodeBidi initialUnicodeBidi() { return UBNormal; }
     static EVisibility initialVisibility() { return VISIBLE; }
-    static EWhiteSpace initialWhiteSpace() { return PRE_LINE; }
+    static EWhiteSpace initialWhiteSpace() { return PRE_WRAP; }
     static short initialHorizontalBorderSpacing() { return 0; }
     static short initialVerticalBorderSpacing() { return 0; }
     static Color initialColor() { return Color::white; }