[WIP] Implement flexbox spec behavior for flex factor sum between 0 and 1

Source/core/layout/LayoutFlexibleBox.cpp

Index: Source/core/layout/LayoutFlexibleBox.cpp
diff --git a/Source/core/layout/LayoutFlexibleBox.cpp b/Source/core/layout/LayoutFlexibleBox.cpp
index 5de6becb21b9f66ef63b7ed635c9bea88309a265..60a4ab688195e947a6d0d4a8753ce4eeda9dd437 100644
--- a/Source/core/layout/LayoutFlexibleBox.cpp
+++ b/Source/core/layout/LayoutFlexibleBox.cpp
@@ -74,6 +74,8 @@ LayoutFlexibleBox::LayoutFlexibleBox(Element* element)
     : LayoutBlock(element)
     , m_orderIterator(this)
     , m_numberOfInFlowChildrenOnFirstLine(-1)
+    , m_originalAvailableFreeSpaceInitialized(false)
+    , m_originalAvailableFreeSpace(0)
 {
     ASSERT(!childrenInline());
 }
@@ -961,6 +963,18 @@ bool LayoutFlexibleBox::resolveFlexibleLengths(FlexSign flexSign, const OrderedF
         if (inflexibleItems.contains(child)) {
             childSizes.append(inflexibleItems.get(child));
         } else {
+            if (!m_originalAvailableFreeSpaceInitialized) {
+                m_originalAvailableFreeSpace = availableFreeSpace;
+                m_originalAvailableFreeSpaceInitialized = true;
+            }
+            if (totalFlexGrow < 1.0f) {
+                LayoutUnit desiredPortionOfOriginalFreeSpace = LayoutUnit(m_originalAvailableFreeSpace * totalFlexGrow);
+                if (availableFreeSpace > 0)
+                    availableFreeSpace = std::min(availableFreeSpace, desiredPortionOfOriginalFreeSpace);
+                else
+                    availableFreeSpace = std::max(availableFreeSpace, desiredPortionOfOriginalFreeSpace);
+            }
+
             LayoutUnit childInnerFlexBaseSize = computeInnerFlexBaseSizeForChild(*child);
             LayoutUnit childSize = childInnerFlexBaseSize;
             double extraSpace = 0;