tests: Move ResourcesTest into component test.

Although the tests were initially written for checking the validity of
the text images, it doesn't hurt to run them continuously as part of the
component test (recovery_manual_test requires reboots during the run,
due to the nature of the tests of recovery-{refresh,persist}). This also
allows detecting breaking changes to libminui or libpng.

There's a catch that the ResourcesTest won't be triggered via `atest`,
as the res-* testdata won't be picked up via AndroidTest.xml. Explored
a few options but not addressing that in this CL:
- `atest` is not fully working in AOSP yet (missing support in
  tools/tradefederation/core/atest/atest.py).
- `atest` doesn't allow specifying the testdata with path in the 'push'
  option.
- It won't fail the test run though, as ResourcesTest will skip the
  tests automatically when it finds no text image file.
- APCT and manual `adb sync data` are not affected, and I don't see an
  active user of `atest` other than a tool for manual test invocation.
- Unrelated to this CL, `atest` doesn't seem to work well with
  recovery_component_test or recovery_unit_test while we have both of
  them in one AndroidTest.xml. It randomly triggers only one of them,
  despite of the given test name. When splitting AndroidTest.xml into
  two, it tends to pick up the wrong testdata subdir and gives wrong
  results.

Test: Run recovery_manual_test and recovery_component_test on marlin.
Change-Id: I3a237499a7770356e14085674bc8b9cb4551db85
diff --git a/tests/component/resources_test.cpp b/tests/component/resources_test.cpp
new file mode 100644
index 0000000..618d5a4
--- /dev/null
+++ b/tests/component/resources_test.cpp
@@ -0,0 +1,120 @@
+/*
+ * 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 <dirent.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#include <memory>
+#include <string>
+#include <vector>
+
+#include <android-base/file.h>
+#include <android-base/strings.h>
+#include <gtest/gtest.h>
+#include <png.h>
+
+#include "minui/minui.h"
+#include "private/resources.h"
+
+static const std::string kLocale = "zu";
+
+static const std::vector<std::string> kResourceImagesDirs{ "res-mdpi/images/", "res-hdpi/images/",
+                                                           "res-xhdpi/images/",
+                                                           "res-xxhdpi/images/",
+                                                           "res-xxxhdpi/images/" };
+
+static int png_filter(const dirent* de) {
+  if (de->d_type != DT_REG || !android::base::EndsWith(de->d_name, "_text.png")) {
+    return 0;
+  }
+  return 1;
+}
+
+// Finds out all the PNG files to test, which stay under the same dir with the executabl..
+static std::vector<std::string> add_files() {
+  std::vector<std::string> files;
+  for (const std::string& images_dir : kResourceImagesDirs) {
+    static std::string exec_dir = android::base::GetExecutableDirectory();
+    std::string dir_path = exec_dir + "/" + images_dir;
+    dirent** namelist;
+    int n = scandir(dir_path.c_str(), &namelist, png_filter, alphasort);
+    if (n == -1) {
+      printf("Failed to scandir %s: %s\n", dir_path.c_str(), strerror(errno));
+      continue;
+    }
+    if (n == 0) {
+      printf("No file is added for test in %s\n", dir_path.c_str());
+    }
+
+    while (n--) {
+      std::string file_path = dir_path + namelist[n]->d_name;
+      files.push_back(file_path);
+      free(namelist[n]);
+    }
+    free(namelist);
+  }
+  return files;
+}
+
+class ResourcesTest : public testing::TestWithParam<std::string> {
+ public:
+  static std::vector<std::string> png_list;
+
+ protected:
+  void SetUp() override {
+    png_ = std::make_unique<PngHandler>(GetParam());
+    ASSERT_TRUE(png_);
+
+    ASSERT_EQ(PNG_COLOR_TYPE_GRAY, png_->color_type()) << "Recovery expects grayscale PNG file.";
+    ASSERT_LT(static_cast<png_uint_32>(5), png_->width());
+    ASSERT_LT(static_cast<png_uint_32>(0), png_->height());
+    ASSERT_EQ(1, png_->channels()) << "Recovery background text images expects 1-channel PNG file.";
+  }
+
+  std::unique_ptr<PngHandler> png_{ nullptr };
+};
+
+// Parses a png file and tests if it's qualified for the background text image under recovery.
+TEST_P(ResourcesTest, ValidateLocale) {
+  std::vector<unsigned char> row(png_->width());
+  for (png_uint_32 y = 0; y < png_->height(); ++y) {
+    png_read_row(png_->png_ptr(), row.data(), nullptr);
+    int w = (row[1] << 8) | row[0];
+    int h = (row[3] << 8) | row[2];
+    int len = row[4];
+    EXPECT_LT(0, w);
+    EXPECT_LT(0, h);
+    EXPECT_LT(0, len) << "Locale string should be non-empty.";
+    EXPECT_NE(0, row[5]) << "Locale string is missing.";
+
+    ASSERT_GT(png_->height(), y + 1 + h) << "Locale: " << kLocale << " is not found in the file.";
+    char* loc = reinterpret_cast<char*>(&row[5]);
+    if (matches_locale(loc, kLocale.c_str())) {
+      EXPECT_TRUE(android::base::StartsWith(loc, kLocale));
+      break;
+    }
+    for (int i = 0; i < h; ++i, ++y) {
+      png_read_row(png_->png_ptr(), row.data(), nullptr);
+    }
+  }
+}
+
+std::vector<std::string> ResourcesTest::png_list = add_files();
+
+INSTANTIATE_TEST_CASE_P(BackgroundTextValidation, ResourcesTest,
+                        ::testing::ValuesIn(ResourcesTest::png_list.cbegin(),
+                                            ResourcesTest::png_list.cend()));