Add a mechanism to force parameters of a group to a specific value.

components/variations/variations_associated_data_unittest.cc

Index: components/variations/variations_associated_data_unittest.cc
diff --git a/components/variations/variations_associated_data_unittest.cc b/components/variations/variations_associated_data_unittest.cc
index 21d0ff04d39e6abae9f511408e8b2be36ed72dcb..a0ce2da1e935fe3e3b540b406dc3b0df72ecc1b4 100644
--- a/components/variations/variations_associated_data_unittest.cc
+++ b/components/variations/variations_associated_data_unittest.cc
@@ -356,4 +356,21 @@ TEST_F(VariationsAssociatedDataTest, GetVariationParamValue_ActivatesTrial) {
   ASSERT_TRUE(IsFieldTrialActive(kTrialName));
 }
 
+TEST_F(VariationsAssociatedDataTest, AssociateParamsFromString) {
+  const std::string kTrialName = "AssociateVariationParams";
+  const std::string kVariationsString =
+      "AssociateVariationParams.A:a/10/b/test,AssociateVariationParams.B:a/%2F";
+  ASSERT_TRUE(AssociateParamsFromString(kVariationsString));
+
+  base::FieldTrialList::CreateFieldTrial(kTrialName, "B");
+  EXPECT_EQ("/", GetVariationParamValue(kTrialName, "a"));
+  EXPECT_EQ(std::string(), GetVariationParamValue(kTrialName, "b"));
+  EXPECT_EQ(std::string(), GetVariationParamValue(kTrialName, "x"));
+
+  std::map<std::string, std::string> params;
+  EXPECT_TRUE(GetVariationParams(kTrialName, &params));
+  EXPECT_EQ(1U, params.size());
+  EXPECT_EQ("/", params["a"]);
+}
+
 }  // namespace variations