Fix absolute position if align-item or justify-content is center or f…

…lex-end

Summary:
Fix facebook#310 (```center```)

additionally fixes if ```flex-end``` is set.
Closes facebook/yoga#349

Reviewed By: dshahidehpour

Differential Revision: D4458528

Pulled By: emilsjolander

fbshipit-source-id: f073c80bfc3ea6675cb95b00283074d10e91a042

ReactCommon/yoga/yoga/Yoga.c

@@ -1471,6 +1471,14 @@ static void YGNodeAbsoluteLayoutChild(const YGNodeRef node,
                                                 child->layout.measuredDimensions[dim[mainAxis]] -
                                                 YGNodeTrailingBorder(node, mainAxis) -
                                                 YGNodeTrailingPosition(child, mainAxis, width);
+  } else if (!YGNodeIsLeadingPosDefined(child, mainAxis) &&
+      node->style.justifyContent == YGJustifyCenter) {
+    child->layout.position[leading[mainAxis]] = (node->layout.measuredDimensions[dim[mainAxis]] -
+                                                 child->layout.measuredDimensions[dim[mainAxis]]) / 2.0f;
+  } else if (!YGNodeIsLeadingPosDefined(child, mainAxis) &&
+      node->style.justifyContent == YGJustifyFlexEnd) {
+    child->layout.position[leading[mainAxis]] = (node->layout.measuredDimensions[dim[mainAxis]] -
+                                                 child->layout.measuredDimensions[dim[mainAxis]]);
   }
 
   if (YGNodeIsTrailingPosDefined(child, crossAxis) &&
@@ -1479,6 +1487,14 @@ static void YGNodeAbsoluteLayoutChild(const YGNodeRef node,
                                                  child->layout.measuredDimensions[dim[crossAxis]] -
                                                  YGNodeTrailingBorder(node, crossAxis) -
                                                  YGNodeTrailingPosition(child, crossAxis, width);
+  } else if (!YGNodeIsLeadingPosDefined(child, crossAxis) &&
+    YGNodeAlignItem(node, child) == YGAlignCenter) {
+    child->layout.position[leading[crossAxis]] = (node->layout.measuredDimensions[dim[crossAxis]] -
+                                                  child->layout.measuredDimensions[dim[crossAxis]]) / 2.0f;
+  } else if (!YGNodeIsLeadingPosDefined(child, crossAxis) &&
+    YGNodeAlignItem(node, child) == YGAlignFlexEnd) {
+    child->layout.position[leading[crossAxis]] = (node->layout.measuredDimensions[dim[crossAxis]] -
+                                                  child->layout.measuredDimensions[dim[crossAxis]]);
   }
 }
 
@@ -2785,7 +2801,7 @@ static inline bool YGMeasureModeOldSizeIsUnspecifiedAndStillFits(YGMeasureMode s
                                                                  YGMeasureMode lastSizeMode,
                                                                  float lastComputedSize) {
   return sizeMode == YGMeasureModeAtMost && lastSizeMode == YGMeasureModeUndefined &&
-         size >= lastComputedSize;
+         (size >= lastComputedSize || YGFloatsEqual(size, lastComputedSize));
 }
 
 static inline bool YGMeasureModeNewMeasureSizeIsStricterAndStillValid(YGMeasureMode sizeMode,
@@ -2794,7 +2810,7 @@ static inline bool YGMeasureModeNewMeasureSizeIsStricterAndStillValid(YGMeasureM
                                                                       float lastSize,
                                                                       float lastComputedSize) {
   return lastSizeMode == YGMeasureModeAtMost && sizeMode == YGMeasureModeAtMost &&
-         lastSize > size && lastComputedSize <= size;
+         lastSize > size && (lastComputedSize <= size || YGFloatsEqual(size, lastComputedSize));
 }
 
 bool YGNodeCanUseCachedMeasurement(const YGMeasureMode widthMode,