Use Px in TextLayoutResult class

And also introduce Px.ceil function to be explicitly saying that the
value is ceiled.

Bug: 146156427
Test: ./gradlew test
Test: TreeHugger
Change-Id: I8a5deeddb2ff0146c66525478bbb3cf9299945f0

diff --git a/ui/ui-unit/api/public_plus_experimental_current.txt b/ui/ui-unit/api/public_plus_experimental_current.txt
index a992471..905d27a0 100644
--- a/ui/ui-unit/api/public_plus_experimental_current.txt
+++ b/ui/ui-unit/api/public_plus_experimental_current.txt

@@ -266,6 +266,7 @@
     method public static inline androidx.ui.unit.IntPxSize IntPxSize(androidx.ui.unit.IntPx width, androidx.ui.unit.IntPx height);
     method public static inline androidx.ui.unit.PxPosition PxPosition(androidx.ui.unit.IntPx x, androidx.ui.unit.IntPx y);
     method public static inline androidx.ui.unit.PxSize PxSize(androidx.ui.unit.IntPx width, androidx.ui.unit.IntPx height);
+    method public static inline androidx.ui.unit.IntPx ceil(androidx.ui.unit.Px);
     method public static androidx.ui.unit.IntPxPosition center(androidx.ui.unit.IntPxSize);
     method public static inline androidx.ui.unit.IntPx coerceAtLeast(androidx.ui.unit.IntPx, androidx.ui.unit.IntPx minimumValue);
     method public static inline androidx.ui.unit.IntPx coerceAtMost(androidx.ui.unit.IntPx, androidx.ui.unit.IntPx maximumValue);