Create TimeBase for time related classes.

src/base/bits.h

Index: src/base/bits.h
diff --git a/src/base/bits.h b/src/base/bits.h
index 0e7662488428899bb8ca96677d873fcabac284db..ddac275e606a9f47706953e8f4af570acd0603c0 100644
--- a/src/base/bits.h
+++ b/src/base/bits.h
@@ -7,6 +7,7 @@
 
 #include <stdint.h>
 #include "src/base/macros.h"
+#include "src/base/safe_math.h"
 #if V8_CC_MSVC
 #include <intrin.h>
 #endif
@@ -296,6 +297,29 @@ inline uint32_t UnsignedMod32(uint32_t lhs, uint32_t rhs) {
   return rhs ? lhs % rhs : 0u;
 }
 
+
+// Clamp |value| on overflow and underflow conditions.
+int64_t FromCheckedNumeric(const CheckedNumeric<int64_t> value);
+
+
+// SignedSaturatedAdd64(lhs, rhs) adds |lhs| and |rhs|,
+// checks and returns the result.
+inline int64_t SignedSaturatedAdd64(int64_t lhs, int64_t rhs) {
+  CheckedNumeric<int64_t> rv(lhs);

[Benedikt Meurer, 2016/05/06 05:12:58]

Please move the implementation and therefore the use of CheckedNumeric into the
bits.cc file.

[lpy, 2016/05/06 05:28:29]

Done.

+  rv += rhs;
+  return FromCheckedNumeric(rv);
+}
+
+
+// SignedSaturatedSub64(lhs, rhs) substracts |lhs| by |rhs|,
+// checks and returns the result.
+inline int64_t SignedSaturatedSub64(int64_t lhs, int64_t rhs) {
+  CheckedNumeric<int64_t> rv(lhs);

[Benedikt Meurer, 2016/05/06 05:12:58]

See comment above.

[lpy, 2016/05/06 05:28:29]

Done.

+  rv -= rhs;
+  return FromCheckedNumeric(rv);
+}
+
+
 }  // namespace bits
 }  // namespace base
 }  // namespace v8