[css-flexbox] Cache whether our main axis size is definite

third_party/WebKit/Source/core/layout/LayoutFlexibleBox.cpp

Index: third_party/WebKit/Source/core/layout/LayoutFlexibleBox.cpp
diff --git a/third_party/WebKit/Source/core/layout/LayoutFlexibleBox.cpp b/third_party/WebKit/Source/core/layout/LayoutFlexibleBox.cpp
index a6a1db68676a4229937e685667849be1d328e084..055c934452d966e9ee79c2668f68bc884859396f 100644
--- a/third_party/WebKit/Source/core/layout/LayoutFlexibleBox.cpp
+++ b/third_party/WebKit/Source/core/layout/LayoutFlexibleBox.cpp
@@ -90,6 +90,7 @@ LayoutFlexibleBox::LayoutFlexibleBox(Element* element)
     : LayoutBlock(element)
     , m_orderIterator(this)
     , m_numberOfInFlowChildrenOnFirstLine(-1)
+    , m_hasDefiniteHeight(-1)
 {
     ASSERT(!childrenInline());
 }
@@ -337,6 +338,10 @@ void LayoutFlexibleBox::layoutBlock(bool relayoutChildren)
     if (!relayoutChildren && simplifiedLayout())
         return;
 
+    LayoutBox* firstChild = firstInFlowChildBox();
+    if (firstChild)
+        m_hasDefiniteHeight = firstChild->computePercentageLogicalHeight(Length(0, Percent)) != LayoutUnit(-1);
+
     m_relaidOutChildren.clear();
 
     if (updateLogicalWidthAndColumnWidth())
@@ -380,6 +385,10 @@ void LayoutFlexibleBox::layoutBlock(bool relayoutChildren)
     updateAfterLayout();
 
     clearNeedsLayout();
+
+    // We have to reset this, because changes to our ancestors' style
+    // can affect this value.
+    m_hasDefiniteHeight = -1;
 }
 
 void LayoutFlexibleBox::paintChildren(const PaintInfo& paintInfo, const LayoutPoint& paintOffset) const
@@ -769,9 +778,11 @@ bool LayoutFlexibleBox::mainAxisLengthIsDefinite(const LayoutBox& child, const L
     if (flexBasis.isAuto())
         return false;
     if (flexBasis.hasPercent()) {
-        return isColumnFlow() ?
-            child.computePercentageLogicalHeight(flexBasis) != -1 :
-            true;
+        if (!isColumnFlow() || m_hasDefiniteHeight == 1)
+            return true;
+        if (m_hasDefiniteHeight == 0)
+            return false;
+        return child.computePercentageLogicalHeight(flexBasis) != -1;
     }
     return true;
 }
@@ -781,9 +792,11 @@ bool LayoutFlexibleBox::crossAxisLengthIsDefinite(const LayoutBox& child, const
     if (length.isAuto())
         return false;
     if (length.hasPercent()) {
-        return hasOrthogonalFlow(child) ?
-            true :
-            child.computePercentageLogicalHeight(length) != -1;
+        if (hasOrthogonalFlow(child) || m_hasDefiniteHeight == 1)
+            return true;
+        if (m_hasDefiniteHeight == 0)
+            return false;
+        return child.computePercentageLogicalHeight(length) != -1;
     }
     // TODO(cbiesinger): Eventually we should support other types of sizes here. Requires updating
     // computeMainSizeFromAspectRatioUsing.
@@ -1149,7 +1162,6 @@ LayoutUnit LayoutFlexibleBox::mainSizeForPercentageResolution(const LayoutBox& c
         // If flex basis had a percentage, our size is guaranteed to be definite or the flex item's
         // size could not be definite.
         // Otherwise, we make up a percentage to check whether we have a definite size.
-        // TODO(cbiesinger): cache this somewhere
         if (!mainAxisLengthIsDefinite(child, Length(0, Percent)))
             return LayoutUnit(-1);
     }