Fix Android path to request media scan for removable media.

In Android, a removable media labelled as "UNTITLED" is mounted
at /storage/removable_UNTITLED instead of /storage/UNTITLED.
This behavior change was made by ag/6513597, but Chrome side
didn't follow the changed paths.

*Example*
CrOS path: /removable/media/UNTITLED/foo.jpg
Wrong path to request media scan (today's behavior): /storage/UNTITLED/foo.jpg
Correct path to request media scan: /storage/removable_UNTITLED/foo.jpg

This CL alters the path in Chrome side, since Android side
can't tell if the requested path is on a removable device or not.

Bug: 1000163
Test: Manually tested on Kevin.
Change-Id: I318735135900ed47f144bff13a51965b0bcb0ee0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1787620
Commit-Queue: Naoki Fukino <fukino@chromium.org>
Reviewed-by: Yusuke Sato <yusukes@chromium.org>
Reviewed-by: Ryo Hashimoto <hashimoto@chromium.org>
Cr-Commit-Position: refs/heads/master@{#694192}

chrome/browser/chromeos/arc/file_system_watcher/arc_file_system_watcher_service.cc

@@ -66,6 +66,11 @@ constexpr base::FilePath::CharType kCrosRemovableMediaDir[] =
 constexpr base::FilePath::CharType kAndroidRemovableMediaDir[] =
     FILE_PATH_LITERAL("/storage");
 
+// The prefix for device label used in Android paths for removable media.
+// A removable device mounted at /media/removable/UNTITLED is mounted at
+// /storage/removable_UNTITLED in Android.
+constexpr char kRemovableMediaLabelPrefix[] = "removable_";
+
 // How long to wait for new inotify events before building the updated timestamp
 // map.
 const base::TimeDelta kBuildTimestampMapDelay =
@@ -126,7 +131,11 @@ TimestampMap BuildTimestampMap(base::FilePath cros_dir,
     // Android file path can be obtained by replacing |cros_dir|
     // prefix with |android_dir|.
     base::FilePath android_path(android_dir);
-    cros_dir.AppendRelativePath(cros_path, &android_path);
+    if (cros_dir.value() == kCrosRemovableMediaDir) {
+      AppendRelativePathForRemovableMedia(cros_path, &android_path);
+    } else {
+      cros_dir.AppendRelativePath(cros_path, &android_path);
+    }
     const base::FileEnumerator::FileInfo& info = enumerator.GetInfo();
     timestamp_map[android_path] = info.GetLastModifiedTime();
   }
@@ -251,6 +260,35 @@ bool HasAndroidSupportedMediaExtension(const base::FilePath& path) {
       extension.c_str(), less_comparator);
 }
 
+bool AppendRelativePathForRemovableMedia(const base::FilePath& cros_path,
+                                         base::FilePath* android_path) {
+  std::vector<base::FilePath::StringType> parent_components;
+  base::FilePath(kCrosRemovableMediaDir).GetComponents(&parent_components);
+  std::vector<base::FilePath::StringType> child_components;
+  cros_path.GetComponents(&child_components);
+  auto child_itr = child_components.begin();
+  for (const auto& parent_component : parent_components) {
+    if (child_itr == child_components.end() || parent_component != *child_itr) {
+      LOG(WARNING) << "|cros_path| is not under kCrosRemovableMediaDir.";
+      return false;
+    }
+    ++child_itr;
+  }
+  if (child_itr == child_components.end()) {
+    LOG(WARNING) << "The CrOS path doesn't have a component for device label.";
+    return false;
+  }
+  // The device label (e.g. "UNTITLED" for /media/removable/UNTITLED/foo.jpg)
+  // should be converted to removable_UNTITLED, since the prefix "removable_"
+  // is appended to paths for removable media in Android.
+  *android_path = android_path->Append(kRemovableMediaLabelPrefix + *child_itr);
+  ++child_itr;
+  for (; child_itr != child_components.end(); ++child_itr) {
+    *android_path = android_path->Append(*child_itr);
+  }
+  return true;
+}
+
 // The core part of ArcFileSystemWatcherService to watch for file changes in
 // directory.
 class ArcFileSystemWatcherService::FileSystemWatcher {

chrome/browser/chromeos/arc/file_system_watcher/arc_file_system_watcher_service.h

@@ -32,6 +32,12 @@ class ArcBridgeService;
 // Returns true if the file path has a media extension supported by Android.
 bool HasAndroidSupportedMediaExtension(const base::FilePath& path);
 
+// Appends |cros_path|'s relative path from "/media/removable" to |android_path|
+// with the altered device label which is used in Android removable media paths.
+// Exposed only for testing.
+bool AppendRelativePathForRemovableMedia(const base::FilePath& cros_path,
+                                         base::FilePath* android_path);
+
 // Exposed only for testing.
 extern const char* kAndroidSupportedMediaExtensions[];
 extern const int kAndroidSupportedMediaExtensionsSize;

chrome/browser/chromeos/arc/file_system_watcher/arc_file_system_watcher_service_unittest.cc

@@ -50,4 +50,39 @@ TEST(ArcFileSystemWatcherServiceTest, HasAndroidSupportedMediaExtension) {
       base::FilePath(FILE_PATH_LITERAL("/tmp/kitten"))));
 }
 
+TEST(ArcFileSystemWatcherServiceTest, AppendRelativePathForRemovableMedia) {
+  base::FilePath android_path(FILE_PATH_LITERAL("/storage"));
+  EXPECT_TRUE(AppendRelativePathForRemovableMedia(
+      base::FilePath(FILE_PATH_LITERAL("/media/removable/UNTITLED/foo.jpg")),
+      &android_path));
+  EXPECT_EQ("/storage/removable_UNTITLED/foo.jpg", android_path.value());
+
+  android_path = base::FilePath(FILE_PATH_LITERAL("/storage"));
+  EXPECT_TRUE(AppendRelativePathForRemovableMedia(
+      base::FilePath(
+          FILE_PATH_LITERAL("/media/removable/UNTITLED/foo/bar/baz.mp4")),
+      &android_path));
+  EXPECT_EQ("/storage/removable_UNTITLED/foo/bar/baz.mp4",
+            android_path.value());
+
+  android_path = base::FilePath(FILE_PATH_LITERAL("/"));
+  EXPECT_TRUE(AppendRelativePathForRemovableMedia(
+      base::FilePath(FILE_PATH_LITERAL("/media/removable/UNTITLED/foo.jpg")),
+      &android_path));
+  EXPECT_EQ("/removable_UNTITLED/foo.jpg", android_path.value());
+
+  // Error: |cros_path| is not under /media/removable.
+  android_path = base::FilePath(FILE_PATH_LITERAL("/storage"));
+  EXPECT_FALSE(AppendRelativePathForRemovableMedia(
+      base::FilePath(FILE_PATH_LITERAL("/foo/bar/UNTITLED/foo.jpg")),
+      &android_path));
+  EXPECT_EQ("/storage", android_path.value());
+
+  // Error: |cros_path| does not contain a component for device label.
+  android_path = base::FilePath(FILE_PATH_LITERAL("/storage"));
+  EXPECT_FALSE(AppendRelativePathForRemovableMedia(
+      base::FilePath(FILE_PATH_LITERAL("/media/removable")), &android_path));
+  EXPECT_EQ("/storage", android_path.value());
+}
+
 }  // namespace arc