Inline to make OsStr::is_empty zero cost

Author: tesuji

src/libstd/ffi/os_str.rs

@@ -615,6 +615,7 @@ impl OsStr {
     /// assert!(!os_str.is_empty());
     /// ```
     #[stable(feature = "osstring_simple_functions", since = "1.9.0")]
+    #[inline]
     pub fn is_empty(&self) -> bool {
         self.inner.inner.is_empty()
     }

src/libstd/sys_common/os_str_bytes.rs

@@ -104,6 +104,7 @@ impl Buf {
         self.inner.shrink_to(min_capacity)
     }
 
+    #[inline]
     pub fn as_slice(&self) -> &Slice {
         unsafe { mem::transmute(&*self.inner) }
     }