Quash a whole bunch of warnings

llvm-svn: 145624
Cr-Mirrored-From: sso://chromium.googlesource.com/_direct/external/github.com/llvm/llvm-project
Cr-Mirrored-Commit: c206366fd7774aff222578c2680b931a4c2c35ba
diff --git a/src/chrono.cpp b/src/chrono.cpp
index 416b950..73c83ee 100644
--- a/src/chrono.cpp
+++ b/src/chrono.cpp
@@ -61,7 +61,7 @@
 steady_clock::rep
 steady_simplified()
 {
-    return mach_absolute_time();
+    return static_cast<steady_clock::rep>(mach_absolute_time());
 }
 
 static