create GrTestUtils.h, move some common functions into it

src/gpu/GrTestUtils.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 "GrTestUtils.h"
+#include "SkMatrix.h"
+
+namespace GrTest {
+const SkMatrix& TestMatrix(SkRandom* random) {
+    static SkMatrix gMatrices[5];
+    static bool gOnce;
+    if (!gOnce) {
+        gMatrices[0].reset();
+        gMatrices[1].setTranslate(SkIntToScalar(-100), SkIntToScalar(100));
+        gMatrices[2].setRotate(SkIntToScalar(17));
+        gMatrices[3].setRotate(SkIntToScalar(185));
+        gMatrices[3].postTranslate(SkIntToScalar(66), SkIntToScalar(-33));
+        gMatrices[3].postScale(SkIntToScalar(2), SK_ScalarHalf);
+        gMatrices[4].setRotate(SkIntToScalar(215));
+        gMatrices[4].set(SkMatrix::kMPersp0, 0.00013f);
+        gMatrices[4].set(SkMatrix::kMPersp1, -0.000039f);
+        gOnce = true;
+    }
+    return gMatrices[random->nextULessThan(static_cast<uint32_t>(SK_ARRAY_COUNT(gMatrices)))];
+}
+};