For flex items, percent paddings should resolve against their respective dimension

Source/core/rendering/RenderBoxModelObject.h

Index: Source/core/rendering/RenderBoxModelObject.h
diff --git a/Source/core/rendering/RenderBoxModelObject.h b/Source/core/rendering/RenderBoxModelObject.h
index 8f0c0b5c7b85178c2c1d3bb1f4df44a4bc9ddffd..349f880fff50a72f0591cf7443dfa0a03402d146 100644
--- a/Source/core/rendering/RenderBoxModelObject.h
+++ b/Source/core/rendering/RenderBoxModelObject.h
@@ -48,6 +48,17 @@ enum ContentChangeType {
     CanvasContextChanged
 };
 
+enum PaddingType {
+    TopPadding,
+    RightPadding,
+    BottomPadding,
+    LeftPadding,
+    BeforePadding,
+    AfterPadding,
+    StartPadding,
+    EndPadding
+};
+
 class RenderTextFragment;
 
 // This class is the base for all objects that adhere to the CSS box model as described
@@ -81,14 +92,14 @@ public:
     virtual IntRect borderBoundingBox() const = 0;
 
     // These return the CSS computed padding values.
-    LayoutUnit computedCSSPaddingTop() const { return computedCSSPadding(style()->paddingTop()); }
-    LayoutUnit computedCSSPaddingBottom() const { return computedCSSPadding(style()->paddingBottom()); }
-    LayoutUnit computedCSSPaddingLeft() const { return computedCSSPadding(style()->paddingLeft()); }
-    LayoutUnit computedCSSPaddingRight() const { return computedCSSPadding(style()->paddingRight()); }
-    LayoutUnit computedCSSPaddingBefore() const { return computedCSSPadding(style()->paddingBefore()); }
-    LayoutUnit computedCSSPaddingAfter() const { return computedCSSPadding(style()->paddingAfter()); }
-    LayoutUnit computedCSSPaddingStart() const { return computedCSSPadding(style()->paddingStart()); }
-    LayoutUnit computedCSSPaddingEnd() const { return computedCSSPadding(style()->paddingEnd()); }
+    LayoutUnit computedCSSPaddingTop() const { return computedCSSPadding(style()->paddingTop(), TopPadding); }
+    LayoutUnit computedCSSPaddingBottom() const { return computedCSSPadding(style()->paddingBottom(), BottomPadding); }
+    LayoutUnit computedCSSPaddingLeft() const { return computedCSSPadding(style()->paddingLeft(), LeftPadding); }
+    LayoutUnit computedCSSPaddingRight() const { return computedCSSPadding(style()->paddingRight(), RightPadding); }
+    LayoutUnit computedCSSPaddingBefore() const { return computedCSSPadding(style()->paddingBefore(), BeforePadding); }
+    LayoutUnit computedCSSPaddingAfter() const { return computedCSSPadding(style()->paddingAfter(), AfterPadding); }
+    LayoutUnit computedCSSPaddingStart() const { return computedCSSPadding(style()->paddingStart(), StartPadding); }
+    LayoutUnit computedCSSPaddingEnd() const { return computedCSSPadding(style()->paddingEnd(), EndPadding); }
 
     // These functions are used during layout. Table cells
     // override them to include some extra intrinsic padding.
@@ -297,11 +308,14 @@ public:
     IntSize calculateImageIntrinsicDimensions(StyleImage*, const IntSize& scaledPositioningAreaSize, ScaleByEffectiveZoomOrNot) const;
 
 private:
-    LayoutUnit computedCSSPadding(const Length&) const;
+    LayoutUnit computedCSSPadding(const Length&, PaddingType) const;
     virtual bool isBoxModelObject() const OVERRIDE FINAL { return true; }
 
     IntSize calculateFillTileSize(const FillLayer*, const IntSize& scaledPositioningAreaSize) const;
 
+    LayoutUnit containingBlockLogicalHeightForContent() const;
+    LayoutUnit computePercentLogicalHeight() const;
+
     RoundedRect getBackgroundRoundedRect(const LayoutRect&, InlineFlowBox*, LayoutUnit inlineBoxWidth, LayoutUnit inlineBoxHeight,
         bool includeLogicalLeftEdge, bool includeLogicalRightEdge) const;