vb: also thread --key through to .json

tools/VisualBench/VisualLightweightBenchModule.cpp

Index: tools/VisualBench/VisualLightweightBenchModule.cpp
diff --git a/tools/VisualBench/VisualLightweightBenchModule.cpp b/tools/VisualBench/VisualLightweightBenchModule.cpp
index bc592a3934d564a18b29fdf6419f1dbc7622740c..7b7cdbbeb76abf92ac5f9b7a6512f607ace5ee5c 100644
--- a/tools/VisualBench/VisualLightweightBenchModule.cpp
+++ b/tools/VisualBench/VisualLightweightBenchModule.cpp
@@ -31,8 +31,9 @@ DEFINE_int32(samples, 10, "Number of times to time each skp.");
 DEFINE_int32(frames, 5, "Number of frames of each skp to render per sample.");
 DEFINE_double(loopMs, 5, "Target loop time in millseconds.");
 DEFINE_bool2(verbose, v, false, "enable verbose output from the test driver.");
-DEFINE_string(key, "", "");  // dummy to enable gm tests that have platform-specific names
 DEFINE_string(outResultsFile, "", "If given, write results here as JSON.");
+DEFINE_string(key, "",
+              "Space-separated key/value pairs to add to JSON identifying this builder.");
 DEFINE_string(properties, "",
               "Space-separated key/value pairs to add to JSON identifying this run.");
 
@@ -63,6 +64,14 @@ VisualLightweightBenchModule::VisualLightweightBenchModule(VisualBench* owner)
         fResults.reset(new NanoJSONResultsWriter(FLAGS_outResultsFile[0]));
     }
 
+    if (1 == FLAGS_key.count() % 2) {
+        SkDebugf("ERROR: --key must be passed with an even number of arguments.\n");
+    } else {
+        for (int i = 1; i < FLAGS_key.count(); i += 2) {
+            fResults->key(FLAGS_key[i - 1], FLAGS_key[i]);
+        }
+    }
+
     if (1 == FLAGS_properties.count() % 2) {
         SkDebugf("ERROR: --properties must be passed with an even number of arguments.\n");
     } else {