Adds Server Previews protocol UMA plus UMA for not accepting previews

components/data_reduction_proxy/core/browser/data_reduction_proxy_config_unittest.cc

Index: components/data_reduction_proxy/core/browser/data_reduction_proxy_config_unittest.cc
diff --git a/components/data_reduction_proxy/core/browser/data_reduction_proxy_config_unittest.cc b/components/data_reduction_proxy/core/browser/data_reduction_proxy_config_unittest.cc
index 3d9e073a4e2d61d1788300b4c70ad29b74280cf7..58fd26b36ec1dd9c864d96145be1f19bbb7e272c 100644
--- a/components/data_reduction_proxy/core/browser/data_reduction_proxy_config_unittest.cc
+++ b/components/data_reduction_proxy/core/browser/data_reduction_proxy_config_unittest.cc
@@ -1545,6 +1545,7 @@ TEST_F(DataReductionProxyConfigTest, ShouldAcceptServerPreview) {
   scoped_feature_list.InitAndEnableFeature(
       features::kDataReductionProxyDecidesTransform);
 
+  base::HistogramTester histogram_tester;
   net::TestURLRequestContext context_;
   net::TestDelegate delegate_;
   std::unique_ptr<net::URLRequest> request = context_.CreateRequest(
@@ -1565,6 +1566,9 @@ TEST_F(DataReductionProxyConfigTest, ShouldAcceptServerPreview) {
       switches::kDataReductionProxyLoFiValueDisabled);
   EXPECT_FALSE(config()->ShouldAcceptServerPreview(*request.get(),
                                                    *previews_decider.get()));
+  histogram_tester.ExpectBucketCount(
+      "DataReductionProxy.Protocol.NotAcceptingTransform",
+      0 /* NOT_ACCEPTING_TRANSFORM_DISABLED */, 1);
 
   // Verify true for Slow Connection flag.
   base::CommandLine::ForCurrentProcess()->InitFromArgv(0, NULL);
@@ -1583,6 +1587,9 @@ TEST_F(DataReductionProxyConfigTest, ShouldAcceptServerPreview) {
       net::NetworkChangeNotifier::ConnectionType::CONNECTION_WIFI);
   EXPECT_FALSE(config()->ShouldAcceptServerPreview(*request.get(),
                                                    *previews_decider.get()));
+  histogram_tester.ExpectBucketCount(
+      "DataReductionProxy.Protocol.NotAcceptingTransform",
+      2 /* NOT_ACCEPTING_TRANSFORM_DISABLED */, 1);
 
   // Verify true for Cellular Only flag and 3G connection.
   config()->SetConnectionTypeForTesting(
@@ -1601,6 +1608,9 @@ TEST_F(DataReductionProxyConfigTest, ShouldAcceptServerPreview) {
         "DataReductionProxyPreviewsBlackListTransition", "Enabled");
     EXPECT_FALSE(config()->ShouldAcceptServerPreview(*request.get(),
                                                      *previews_decider.get()));
+    histogram_tester.ExpectBucketCount(
+        "DataReductionProxy.Protocol.NotAcceptingTransform",
+        1 /* NOT_ACCEPTING_TRANSFORM_BLACKLISTED */, 1);
     previews_decider = base::MakeUnique<TestPreviewsDecider>(true);
     EXPECT_TRUE(config()->ShouldAcceptServerPreview(*request.get(),
                                                     *previews_decider.get()));