skpbench: add option for gpu timing

tools/gpu/GpuTimer.h

Index: tools/gpu/GpuTimer.h
diff --git a/tools/gpu/GpuTimer.h b/tools/gpu/GpuTimer.h
new file mode 100644
index 0000000000000000000000000000000000000000..7678421ca6f5db2e246eb4c23b4e0ec2f67a3848
--- /dev/null
+++ b/tools/gpu/GpuTimer.h
@@ -0,0 +1,77 @@
+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef GpuTimer_DEFINED
+#define GpuTimer_DEFINED
+
+#include "SkTypes.h"
+#include "SkExchange.h"
+#include <chrono>
+
+namespace sk_gpu_test {
+
+using PlatformTimerQuery = uint64_t;
+static constexpr PlatformTimerQuery kInvalidTimerQuery = 0;
+
+/**
+ * Platform-independent interface for timing operations on the GPU.
+ */
+class GpuTimer {
+public:
+    GpuTimer(bool disjointSupport)
+        : fDisjointSupport(disjointSupport)
+        , fActiveTimer(kInvalidTimerQuery) {
+    }
+    virtual ~GpuTimer() { SkASSERT(!fActiveTimer); }
+
+    /**
+     * Returns whether this timer can detect disjoint GPU operations while timing. If false, a query
+     * has less confidence when it completes with QueryStatus::kAccurate.
+     */
+    bool disjointSupport() const { return fDisjointSupport; }
+
+    /**
+     * Inserts a "start timing" command in the GPU command stream.
+     */
+    void queueStart() {
+        SkASSERT(!fActiveTimer);
+        fActiveTimer = this->onQueueTimerStart();
+    }
+
+    /**
+     * Inserts a "stop timing" command in the GPU command stream.
+     *
+     * @return a query object that can retrieve the time elapsed once the timer has completed.
+     */
+    PlatformTimerQuery SK_WARN_UNUSED_RESULT queueStop() {
+        SkASSERT(fActiveTimer);
+        this->onQueueTimerStop(fActiveTimer);
+        return skstd::exchange(fActiveTimer, kInvalidTimerQuery);
+    }
+
+    enum class QueryStatus {
+        kInvalid,  //<! the timer query is invalid.
+        kPending,  //<! the timer is still running on the GPU.
+        kDisjoint, //<! the query is complete, but dubious due to disjoint GPU operations.
+        kAccurate  //<! the query is complete and reliable.
+    };
+
+    virtual QueryStatus checkQueryStatus(PlatformTimerQuery) = 0;
+    virtual std::chrono::nanoseconds getTimeElapsed(PlatformTimerQuery) = 0;
+    virtual void deleteQuery(PlatformTimerQuery) = 0;
+
+private:
+    virtual PlatformTimerQuery onQueueTimerStart() const = 0;
+    virtual void onQueueTimerStop(PlatformTimerQuery) const = 0;
+
+    bool const           fDisjointSupport;
+    PlatformTimerQuery   fActiveTimer;
+};
+
+}  // namespace sk_gpu_test
+
+#endif