Add one-time randomization support for FieldTrial, and the ability to

base/rand_util.h

Index: base/rand_util.h
diff --git a/base/rand_util.h b/base/rand_util.h
index a4ea479e334edad7d181e5b4e27da46744deed11..307ce8a9d74542a20acaefe05446350ad24b0d6c 100644
--- a/base/rand_util.h
+++ b/base/rand_util.h
@@ -27,6 +27,10 @@ BASE_API uint64 RandGenerator(uint64 max);
 // Returns a random double in range [0, 1). Thread-safe.
 BASE_API double RandDouble();
 
+// Given input |bits|, convert with maximum precision to a random
+// double in range [0, 1). Thread-safe.
+BASE_API double BitsToRandDouble(uint64 bits);

[jar (doing other things), 2011/04/21 01:03:50]

This doesn't create a random number, but only converts bits to a floating point
number.  Hence its name probably shouldn't include Rand.
I think this should just go in your file, and is not generally useful [it is
very rare to have to add code to base].

[Jói, 2011/04/21 19:50:33]

Changed to BitsToRandLikeDouble. Still not a great name but beats
BitsToDoubleBetweenZeroAndOne (which still wouldn't be 100% accurate).

As we discussed on the phone, this is not adding code to base, this is
extracting most of the implementation of RandDouble() into a function that can
be reused.  An argument could be made to say this would belong in something like
base/math_util.h but I don't really think that's worth it for now.

+
 }  // namespace base
 
 #endif  // BASE_RAND_UTIL_H_