Use low entropy for studies that send experiment IDs to Google properties.

base/test/mock_entropy_provider.cc

Index: base/test/mock_entropy_provider.cc
diff --git a/base/test/mock_entropy_provider.cc b/base/test/mock_entropy_provider.cc
index a4cc9727ce03bb40ba34e94f45dc51fdabf2cf5a..5ebf19a7c737a71b60fe0af93d48287909fcb655 100644
--- a/base/test/mock_entropy_provider.cc
+++ b/base/test/mock_entropy_provider.cc
@@ -6,12 +6,15 @@
 
 namespace base {
 
+MockEntropyProvider::MockEntropyProvider() : entropy_value_(0.5) {}
+MockEntropyProvider::MockEntropyProvider(double entropy_value)
+    : entropy_value_(entropy_value) {}
 MockEntropyProvider::~MockEntropyProvider() {}
 
 double MockEntropyProvider::GetEntropyForTrial(
     const std::string& trial_name,
     uint32_t randomization_seed) const {
-  return 0.5;
+  return entropy_value_;
 }
 
 }  // namespace base