Add base class for GLTestContext and add new subclass VkTestContext.

tools/gpu/TestContext.h

Index: tools/gpu/TestContext.h
diff --git a/tools/gpu/TestContext.h b/tools/gpu/TestContext.h
new file mode 100644
index 0000000000000000000000000000000000000000..5143b8a6fae352c3c8bea503908288ab41061ece
--- /dev/null
+++ b/tools/gpu/TestContext.h
@@ -0,0 +1,95 @@
+
+/*
+ * 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 TestContext_DEFINED
+#define TestContext_DEFINED
+
+#include "GrTypes.h"
+#include "../private/SkGpuFenceSync.h"
+#include "../private/SkTemplates.h"
+
+namespace sk_gpu_test {
+/**
+ * An offscreen 3D context. This class is intended for Skia's internal testing needs and not
+ * for general use.
+ */
+class TestContext : public SkNoncopyable {
+public:
+    virtual ~TestContext();
+
+    virtual bool isValid() const = 0;
+
+    bool fenceSyncSupport() const { return fFenceSync != nullptr; }
+
+    bool getMaxGpuFrameLag(int *maxFrameLag) const {
+        if (!fFenceSync) {
+            return false;
+        }
+        *maxFrameLag = kMaxFrameLag;
+        return true;
+    }
+
+    void makeCurrent() const;
+
+    virtual GrBackend backend() = 0;
+    virtual GrBackendContext backendContext() = 0;
+
+    /** Swaps front and back buffer (if the context has such buffers) */
+    void swapBuffers();
+
+    /**
+     * The only purpose of this function it to provide a means of scheduling
+     * work on the GPU (since all of the subclasses create primary buffers for
+     * testing that are small and not meant to be rendered to the screen).
+     *
+     * If the platform supports fence syncs (OpenGL 3.2+ or EGL_KHR_fence_sync),
+     * this will not swap any buffers, but rather emulate triple buffer synchronization
+     * using fences.
+     *
+     * Otherwise it will call the platform SwapBuffers method. This may or may
+     * not perform some sort of synchronization, depending on whether the
+     * drawing surface provided by the platform is double buffered.
+     */
+    void waitOnSyncOrSwap();
+
+    /**
+     * This notifies the context that we are deliberately testing abandoning
+     * the context. It is useful for debugging contexts that would otherwise
+     * test that GPU resources are properly deleted. It also allows a debugging
+     * context to test that further API calls are not made by Skia GPU code.
+     */
+    virtual void testAbandon();
+
+    /**
+     * returns the fencesync object owned by this GLTestContext
+     */
+    SkGpuFenceSync *fenceSync() { return fFenceSync; }
+
+protected:
+    SkGpuFenceSync* fFenceSync;
+
+    TestContext();
+
+    /** This should destroy the 3D context. */
+    virtual void teardown();
+
+    virtual void onPlatformMakeCurrent() const = 0;
+    virtual void onPlatformSwapBuffers() const = 0;
+
+private:
+    enum {
+        kMaxFrameLag = 3
+    };
+
+    SkPlatformGpuFence fFrameFences[kMaxFrameLag - 1];
+    int fCurrentFenceIdx;
+
+    typedef SkNoncopyable INHERITED;
+};
+}  // namespace sk_gpu_test
+#endif