minui: Move GRSurface into a class.

This CL adds GRSurface::Create() and dtor for managing the allocated
memory in GRSurface class. It also adds GRSurface::data() that hides the
underlying implementation, with both of const and non-const overloads.
This allows `const GRSurface&` to be more useful - previously it only
ensured a const member variable of `data`, instead of a read-only buffer
it points to.

It also marks the parameters in gr_texticon() and gr_blit() as const, as
they're incoming source that shouldn't be altered. It corrects the type
of gr_draw, which is the sink to be painted on (an earlier attempt was
made in [1], but didn't get the full picture correctly).

[1] https://android-review.googlesource.com/c/platform/bootable/recovery/+/704757/

Test: mmma -j bootable/recovery
Test: recovery_unit_test on marlin
Test: Run graphics test on marlin (fbdev).
Test: Run graphics test on blueline (drm).
Change-Id: I7904df084cd6c08fa04a9da97d01b4b1a6e3a20c
diff --git a/tests/unit/minui_test.cpp b/tests/unit/minui_test.cpp
new file mode 100644
index 0000000..cad6a3d
--- /dev/null
+++ b/tests/unit/minui_test.cpp
@@ -0,0 +1,32 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <stdint.h>
+
+#include <memory>
+
+#include <gtest/gtest.h>
+
+#include "minui/minui.h"
+
+TEST(GRSurfaceTest, Create_aligned) {
+  static constexpr size_t kSurfaceDataAlignment = 8;
+  for (size_t data_size = 100; data_size < 128; data_size++) {
+    std::unique_ptr<GRSurface> surface(GRSurface::Create(data_size));
+    ASSERT_TRUE(surface);
+    ASSERT_EQ(0, reinterpret_cast<uintptr_t>(surface->data()) % kSurfaceDataAlignment);
+  }
+}