Initial CL to create GrBatchTest infrastructure

src/gpu/GrBatchTest.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 "GrBatchTest.h"
+#include "SkRandom.h"
+#include "SkTypes.h"
+
+BATCH_TEST_EXTERN(AAFillRectBatch);
+BATCH_TEST_EXTERN(AAStrokeRectBatch);
+
+static BatchTestFunc gTestBatches[] = {
+    BATCH_TEST_ENTRY(AAFillRectBatch),
+    BATCH_TEST_ENTRY(AAStrokeRectBatch),
+};
+
+GrBatch* GrRandomBatch(SkRandom* random, GrContext* context) {
+    uint32_t index = random->nextULessThan(static_cast<uint32_t>(SK_ARRAY_COUNT(gTestBatches)));
+    BatchTestFunc func = gTestBatches[index];
+    return (*func)(random, context);
+}