Use more RenderBox references in RenderFlexibleBox

RenderFlexibleBox has several methods that take pointers to RenderBox instances
but those methods assumes that the objects will never be NULL. We should replace
them by references. This makes the caller code safer.

This is in continuation to the CL https://codereview.chromium.org/555213002/

Review URL: https://codereview.chromium.org/560583003

git-svn-id: svn://svn.chromium.org/blink/trunk@181922 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/Source/core/rendering/RenderFlexibleBox.h

@@ -107,53 +107,53 @@ private:
     LayoutUnit flowAwarePaddingEnd() const;
     LayoutUnit flowAwarePaddingBefore() const;
     LayoutUnit flowAwarePaddingAfter() const;
-    LayoutUnit flowAwareMarginStartForChild(RenderBox* child) const;
-    LayoutUnit flowAwareMarginEndForChild(RenderBox* child) const;
-    LayoutUnit flowAwareMarginBeforeForChild(RenderBox* child) const;
-    LayoutUnit crossAxisMarginExtentForChild(RenderBox* child) const;
+    LayoutUnit flowAwareMarginStartForChild(RenderBox& child) const;
+    LayoutUnit flowAwareMarginEndForChild(RenderBox& child) const;
+    LayoutUnit flowAwareMarginBeforeForChild(RenderBox& child) const;
+    LayoutUnit crossAxisMarginExtentForChild(RenderBox& child) const;
     LayoutUnit crossAxisScrollbarExtent() const;
-    LayoutUnit crossAxisScrollbarExtentForChild(RenderBox* child) const;
-    LayoutPoint flowAwareLocationForChild(RenderBox* child) const;
+    LayoutUnit crossAxisScrollbarExtentForChild(RenderBox& child) const;
+    LayoutPoint flowAwareLocationForChild(RenderBox& child) const;
     // FIXME: Supporting layout deltas.
-    void setFlowAwareLocationForChild(RenderBox* child, const LayoutPoint&);
-    void adjustAlignmentForChild(RenderBox* child, LayoutUnit);
+    void setFlowAwareLocationForChild(RenderBox& child, const LayoutPoint&);
+    void adjustAlignmentForChild(RenderBox& child, LayoutUnit);
     ItemPosition alignmentForChild(RenderBox& child) const;
-    LayoutUnit mainAxisBorderAndPaddingExtentForChild(RenderBox* child) const;
-    LayoutUnit preferredMainAxisContentExtentForChild(RenderBox* child, bool hasInfiniteLineLength, bool relayoutChildren = false);
+    LayoutUnit mainAxisBorderAndPaddingExtentForChild(RenderBox& child) const;
+    LayoutUnit preferredMainAxisContentExtentForChild(RenderBox& child, bool hasInfiniteLineLength, bool relayoutChildren = false);
     bool childPreferredMainAxisContentExtentRequiresLayout(RenderBox& child, bool hasInfiniteLineLength) const;
     bool needToStretchChildLogicalHeight(RenderBox& child) const;
 
     void layoutFlexItems(bool relayoutChildren);
     LayoutUnit autoMarginOffsetInMainAxis(const OrderedFlexItemList&, LayoutUnit& availableFreeSpace);
-    void updateAutoMarginsInMainAxis(RenderBox* child, LayoutUnit autoMarginOffset);
-    bool hasAutoMarginsInCrossAxis(RenderBox* child) const;
-    bool updateAutoMarginsInCrossAxis(RenderBox* child, LayoutUnit availableAlignmentSpace);
+    void updateAutoMarginsInMainAxis(RenderBox& child, LayoutUnit autoMarginOffset);
+    bool hasAutoMarginsInCrossAxis(RenderBox& child) const;
+    bool updateAutoMarginsInCrossAxis(RenderBox& child, LayoutUnit availableAlignmentSpace);
     void repositionLogicalHeightDependentFlexItems(Vector<LineContext>&);
     LayoutUnit clientLogicalBottomAfterRepositioning();
     void appendChildFrameRects(ChildFrameRects&);
 
-    LayoutUnit availableAlignmentSpaceForChild(LayoutUnit lineCrossAxisExtent, RenderBox*);
-    LayoutUnit availableAlignmentSpaceForChildBeforeStretching(LayoutUnit lineCrossAxisExtent, RenderBox*);
-    LayoutUnit marginBoxAscentForChild(RenderBox*);
+    LayoutUnit availableAlignmentSpaceForChild(LayoutUnit lineCrossAxisExtent, RenderBox& child);
+    LayoutUnit availableAlignmentSpaceForChildBeforeStretching(LayoutUnit lineCrossAxisExtent, RenderBox& child);
+    LayoutUnit marginBoxAscentForChild(RenderBox& child);
 
     LayoutUnit computeChildMarginValue(Length margin);
     void prepareOrderIteratorAndMargins();
-    LayoutUnit adjustChildSizeForMinAndMax(RenderBox*, LayoutUnit childSize);
+    LayoutUnit adjustChildSizeForMinAndMax(RenderBox& child, LayoutUnit childSize);
     // The hypothetical main size of an item is the flex base size clamped according to its min and max main size properties
     bool computeNextFlexLine(OrderedFlexItemList& orderedChildren, LayoutUnit& sumFlexBaseSize, double& totalFlexGrow, double& totalWeightedFlexShrink, LayoutUnit& sumHypotheticalMainSize, bool& hasInfiniteLineLength, bool relayoutChildren);
 
     bool resolveFlexibleLengths(FlexSign, const OrderedFlexItemList&, LayoutUnit& availableFreeSpace, double& totalFlexGrow, double& totalWeightedFlexShrink, InflexibleFlexItemSize&, Vector<LayoutUnit, 16>& childSizes, bool hasInfiniteLineLength);
     void freezeViolations(const Vector<Violation>&, LayoutUnit& availableFreeSpace, double& totalFlexGrow, double& totalWeightedFlexShrink, InflexibleFlexItemSize&, bool hasInfiniteLineLength);
 
-    void resetAutoMarginsAndLogicalTopInCrossAxis(RenderBox*);
+    void resetAutoMarginsAndLogicalTopInCrossAxis(RenderBox& child);
     void setLogicalOverrideSize(RenderBox& child, LayoutUnit childPreferredSize);
-    void prepareChildForPositionedLayout(RenderBox* child, LayoutUnit mainAxisOffset, LayoutUnit crossAxisOffset, PositionedLayoutMode);
+    void prepareChildForPositionedLayout(RenderBox& child, LayoutUnit mainAxisOffset, LayoutUnit crossAxisOffset, PositionedLayoutMode);
     size_t numberOfInFlowPositionedChildren(const OrderedFlexItemList&) const;
     void layoutAndPlaceChildren(LayoutUnit& crossAxisOffset, const OrderedFlexItemList&, const Vector<LayoutUnit, 16>& childSizes, LayoutUnit availableFreeSpace, bool relayoutChildren, Vector<LineContext>&, bool hasInfiniteLineLength);
     void layoutColumnReverse(const OrderedFlexItemList&, LayoutUnit crossAxisOffset, LayoutUnit availableFreeSpace);
     void alignFlexLines(Vector<LineContext>&);
     void alignChildren(const Vector<LineContext>&);
-    void applyStretchAlignmentToChild(RenderBox*, LayoutUnit lineCrossAxisExtent);
+    void applyStretchAlignmentToChild(RenderBox& child, LayoutUnit lineCrossAxisExtent);
     void flipForRightToLeftColumn();
     void flipForWrapReverse(const Vector<LineContext>&, LayoutUnit crossAxisStartEdge);