minui: Fix a wrong arg in calling GRSurface::Create().

This is a bug introduced while refactoring init_display_surface(), in
[1]. As a result, user of res_create_multi_display_surface(), which is
effectively `charger` right now, crashes due to buffer overrun.

This CL fixes the wrong arg and adds a sanity test for
res_create_multi_display_surface(). The testdata (battery_scale.png) is
copied from system/core/healthd/images/battery_scale.png.

[1] commit 44820ac1e3.

Bug: 119122296
Test: Run recovery_unit_test on marlin.
Test: Build and boot into charger mode on blueline. Verify that
      `charger` no longer crashes.
Change-Id: Ib6d083e1512a9c3c6eb63874d26d22658921d693

minui/resources.cpp

@@ -261,7 +261,7 @@ int res_create_multi_display_surface(const char* name, int* frames, int* fps,
   for (int i = 0; i < *frames; ++i) {
     auto height_per_frame = height / *frames;
     auto created_surface =
-        GRSurface::Create(width, height_per_frame, width * 4, 4, width * height_per_frame);
+        GRSurface::Create(width, height_per_frame, width * 4, 4, width * height_per_frame * 4);
     if (!created_surface) {
       result = -8;
       goto exit;

tests/unit/resources_test.cpp

@@ -0,0 +1,37 @@
+/*
+ * 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 <string>
+
+#include <gtest/gtest.h>
+
+#include "common/test_constants.h"
+#include "minui/minui.h"
+
+TEST(ResourcesTest, res_create_multi_display_surface) {
+  GRSurface** frames;
+  int frame_count;
+  int fps;
+  ASSERT_EQ(0, res_create_multi_display_surface(from_testdata_base("battery_scale.png").c_str(),
+                                                &frame_count, &fps, &frames));
+  ASSERT_EQ(6, frame_count);
+  ASSERT_EQ(20, fps);
+
+  for (auto i = 0; i < frame_count; i++) {
+    free(frames[i]);
+  }
+  free(frames);
+}