[css-flexbox] slight improvements to mainSizeForPercentageResolution

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 382d87c48c8c460ef294f8eb247b94af338adc53..b517444e81864051b7b341e750143b5522341242 100644
--- a/third_party/WebKit/Source/core/layout/LayoutFlexibleBox.cpp
+++ b/third_party/WebKit/Source/core/layout/LayoutFlexibleBox.cpp
@@ -1109,9 +1109,14 @@ LayoutUnit LayoutFlexibleBox::mainSizeForPercentageResolution(const LayoutBox& c
     const Length& flexBasis = flexBasisForChild(child);
     if (!mainAxisLengthIsDefinite(child, flexBasis))
         return LayoutUnit(-1);
-    LayoutUnit mainSize = isColumnFlow() ? computeDefiniteLogicalHeight() : computeDefiniteLogicalWidth();
-    if (mainSize == LayoutUnit(-1))
-        return mainSize;
+    if (!flexBasis.hasPercent()) {
+        // 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);
+    }
 
     if (hasOrthogonalFlow(child))
         return child.hasOverrideLogicalContentHeight() ? child.overrideLogicalContentHeight() : LayoutUnit(-1);