Add a control benchmark.

bench/ControlBench.cpp

+/*
+ * Copyright 2015 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "Benchmark.h"
+
+// This benchmark's runtime should be fairly constant for a given machine,
+// so it can be used as a baseline to control for thermal or other throttling.
+
+struct ControlBench : public Benchmark {
+    const char* onGetName() override { return "control"; }
+    bool isSuitableFor(Backend backend) override { return backend == kNonRendering_Backend; }
+
+    void onDraw(const int loops, SkCanvas*) override {
+        // Nothing terribly useful: force a memory read, a memory write, and some math.
+        volatile uint32_t rand = 0;
+        for (int i = 0; i < 1000*loops; i++) {
+            rand *= 1664525;
+            rand += 1013904223;
+        }
+    }
+};
+DEF_BENCH(return new ControlBench;)