nanobench: Add per-run time reporting.

This patch adds per-benchmark-iteration times to our JSON output. Given that we
already collect these statistics, giving them to the user would be nice.

No unit-test provided, since `rgrep -i json tests` yielded nothing. Happy to add
one if someone wants.

BUG=None.
TEST=nanobench now writes per-run timinings with the output JSON.

Change-Id: I910f1d97fd3e0ee69fc8e78e011e67b9c866f18d
Reviewed-on: https://skia-review.googlesource.com/5617
Reviewed-by: Mike Klein <mtklein@chromium.org>
Commit-Queue: Ravi Mistry <rmistry@google.com>

2 files changed, 14 insertions, 0 deletions

diff --git a/bench/ResultsWriter.h b/bench/ResultsWriter.h
index dc50ace560..1d6dc3eef1 100644
--- a/bench/ResultsWriter.h
+++ b/bench/ResultsWriter.h
@@ -47,6 +47,9 @@ public:
     // Record a single test metric.
     virtual void metric(const char name[], double ms) {}
 
+    // Record a list of test metrics.
+    virtual void metrics(const char name[], const SkTArray<double>& array) {}
+
     // Flush to storage now please.
     virtual void flush() {}
 };
@@ -114,6 +117,16 @@ public:
         SkASSERT(fConfig);
         (*fConfig)[name] = ms;
     }
+    void metrics(const char name[], const SkTArray<double>& array) override {
+        SkASSERT(fConfig);
+        Json::Value value = Json::Value(Json::arrayValue);
+        value.resize(array.count());
+        for (int i = 0; i < array.count(); i++) {
+            // Don't care about nan-ness.
+            value[i] = array[i];
+        }
+        (*fConfig)[name] = std::move(value);
+    }
 
     // Flush to storage now please.
     void flush() override {
diff --git a/bench/nanobench.cpp b/bench/nanobench.cpp
index 5abecd64ee..9e641b909c 100644
--- a/bench/nanobench.cpp
+++ b/bench/nanobench.cpp
@@ -1288,6 +1288,7 @@ int nanobench_main() {
             benchStream.fillCurrentOptions(log.get());
             target->fillOptions(log.get());
             log->metric("min_ms",    stats.min);
+            log->metrics("samples",    samples);
 #if SK_SUPPORT_GPU
             if (gpuStatsDump) {
                 // dump to json, only SKPBench currently returns valid keys / values