Add mobile yoga tree captures (facebook#1640)

Summary:
Pull Request resolved: facebook#1640

Added two captures that were captured from a mobile device.

**profile-ios**: A profile-like view with a central picture and some text information underneath. Captured on iOS device
**feed-android** A feed-like view with a scrollable list of images and text. Captured on Android device.

Fixed a bug that would not deserialize undefined values

Reviewed By: NickGerleman

Differential Revision: D55712235

fbshipit-source-id: ed32b393c088c695d8191149c729e51008df4e7e

benchmark/TreeDeserialization.cpp

@@ -21,6 +21,10 @@ static inline bool isAuto(json& j) {
   return j.is_string() && j == "auto";
 }
 
+static inline bool isUndefined(json& j) {
+  return j.is_string() && j == "undefined";
+}
+
 static inline std::string invalidArgumentMessage(
     const std::string& arg,
     const std::string& enumName) {
@@ -142,6 +146,9 @@ YGUnit unitFromJson(json& j) {
   if (isAuto(j)) {
     return YGUnitAuto;
   }
+  if (isUndefined(j)) {
+    return YGUnitUndefined;
+  }
 
   std::string unit = j["unit"];
   if (unit == "px") {