Began logging more gpu stats from nanobench

bench/SKPBench.cpp

Index: bench/SKPBench.cpp
diff --git a/bench/SKPBench.cpp b/bench/SKPBench.cpp
index 910af6b802337a700557f1ceedc24ab5a1375458..c5480904053dbfd98cce060e1860f3bc366f3e61 100644
--- a/bench/SKPBench.cpp
+++ b/bench/SKPBench.cpp
@@ -155,3 +155,41 @@ void SKPBench::drawPicture() {
         fSurfaces[j]->getCanvas()->flush();
     }
 }
+
+#if SK_SUPPORT_GPU
+static void draw_pic_for_stats(SkCanvas* canvas, GrContext* context, const SkPicture* picture,
+                               SkTArray<SkString>* keys, SkTArray<double>* values,
+                               const char* tag) {
+    context->resetGpuStats();
+    canvas->drawPicture(picture);
+    canvas->flush();
+
+    int offset = keys->count();
+    context->dumpGpuStatsKeyValuePairs(keys, values);
+
+    // append tag, but only to new tags
+    for (int i = offset; i < keys->count(); i++, offset++) {
+        (*keys)[i].appendf("_%s", tag);
+    }
+}
+#endif
+
+void SKPBench::getGpuStats(SkCanvas* canvas, SkTArray<SkString>* keys, SkTArray<double>* values) {
+#if SK_SUPPORT_GPU
+    // we do a special single draw and then dump the key / value pairs
+    GrContext* context = canvas->getGrContext();
+    if (!context) {
+        return;
+    }
+
+    // TODO refactor this out if we want to test other subclasses of skpbench
+    context->flush();
+    context->freeGpuResources();
+    context->resetContext();
+    draw_pic_for_stats(canvas, context, fPic, keys, values, "first_frame");
+
+    // draw second frame
+    draw_pic_for_stats(canvas, context, fPic, keys, values, "second_frame");
+
+#endif
+}