Modify rappor parameters.

components/rappor/rappor_parameters.h

Index: components/rappor/rappor_parameters.h
diff --git a/components/rappor/rappor_parameters.h b/components/rappor/rappor_parameters.h
index 77b16146f608cde86001c8af669d1edf03e7979e..6a59c1cd62bfcb21b6bbe99c4d05266f506da74b 100644
--- a/components/rappor/rappor_parameters.h
+++ b/components/rappor/rappor_parameters.h
@@ -12,6 +12,7 @@ namespace rappor {
 enum Probability {
   PROBABILITY_75,    // 75%
   PROBABILITY_50,    // 50%
+  PROBABILITY_25,    // 25%
 };
 
 // An object describing a rappor metric and the parameters used to generate it.
@@ -22,6 +23,11 @@ struct RapporParameters {
   // Get a string representing the parameters, for DCHECK_EQ.
   std::string ToString() const;
 
+  // The maximum number of cohorts we divide clients into.
+  static const int kMaxCohorts = 512;

[Alexei Svitkine (slow), 2014/05/20 06:59:49]

I'm not sure that this syntax is supported by all our compilers. You might need
to set the value in the .cc file instead.

[Steven Holte, 2014/05/20 22:53:53]

Searching turned up the STATIC_CONST_MEMBER_DEFINITION macro which has the
following comment:
// The C++ standard requires that static const members have an out-of-class
// definition (in a single compilation unit), but MSVC chokes on this (when
// language extensions, which are required, are enabled). (You're only likely to
// notice the need for a definition if you take the address of the member or,
// more commonly, pass it to a function that takes it as a reference argument --
// probably an STL function.) This macro makes MSVC do the right thing. See
// http://msdn.microsoft.com/en-us/library/34h23df8(v=vs.100).aspx for more
// information. Use like:
//
// In .h file:
//   struct Foo {
//     static const int kBar = 5;
//   };
//
// In .cc file:
//   STATIC_CONST_MEMBER_DEFINITION const int Foo::kBar;

So I've added the definition to the .cc, but left the value here so it can be
inlined by the compiler.

+  // The number of cohorts to divide the reports for this metric into.
+  int num_cohorts;
+
   // The number of bytes stored in the Bloom filter.
   int bloom_filter_size_bytes;
   // The number of hash functions used in the Bloom filter.