PerfProvider: Get collection parameters from Finch

chrome/browser/metrics/perf/random_selector.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/metrics/perf/random_selector.h"
 
 #include "base/logging.h"
 #include "base/rand_util.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_split.h"
 #include "base/strings/string_util.h"
 
 RandomSelector::RandomSelector() : sum_of_weights_(0) {}
 
 RandomSelector::~RandomSelector() {}
 
+// static
 double RandomSelector::SumWeights(const std::vector<WeightAndValue>& odds) {
   double sum = 0.0;
   for (const auto& odd : odds) {
+    if (odd.weight <= 0.0)
+      return -1.0;
     sum += odd.weight;
   }
   return sum;
 }
 
-void RandomSelector::SetOdds(const std::vector<WeightAndValue>& odds) {
+bool RandomSelector::SetOdds(const std::vector<WeightAndValue>& odds) {
+  double sum = SumWeights(odds);
+  if (sum <= 0.0)
+    return false;
   odds_ = odds;
-  sum_of_weights_ = SumWeights(odds_);
+  sum_of_weights_ = sum;
+  return true;
 }
 
 const std::string& RandomSelector::Select() {
   // Get a random double between 0 and the sum.
   double random = RandDoubleUpTo(sum_of_weights_);
   // Figure out what it belongs to.
   return GetValueFor(random);
 }
 
 double RandomSelector::RandDoubleUpTo(double max) {
   CHECK_GT(max, 0.0);
   return max * base::RandDouble();
 }
 
 const std::string& RandomSelector::GetValueFor(double random) {
   double current = 0.0;
   for (const auto& odd : odds_) {
     current += odd.weight;
     if (random < current)
       return odd.value;
   }
   NOTREACHED() << "Invalid value for key: " << random;
   return base::EmptyString();
 }
+
+// Print the value. Used for friendly test failure messages.
+::std::ostream& operator<<(
+    ::std::ostream& os, const RandomSelector::WeightAndValue& value) {
+  return os << "{" << value.weight << ", \"" << value.value << "\"}";
+}