Fix unmatching type

Missed a slightly mismatched type (int vs int32_t) from a previous code
review.

Change-Id: Ib56775a3a1a6ec3763da7f7432186954251cc048

engine/src/flutter/libs/minikin/Layout.cpp

@@ -81,7 +81,7 @@ private:
     float mSize;
     float mScaleX;
     float mSkewX;
-    int mPaintFlags;
+    int32_t mPaintFlags;
     bool mIsRtl;
     // Note: any fields added to MinikinPaint must also be reflected here.
     // TODO: language matching (possibly integrate into style)