Download WebAPK into a WebAPK-specifc directory, and delete all cached ones.

chrome/browser/android/webapk/webapk_installer.cc

Index: chrome/browser/android/webapk/webapk_installer.cc
diff --git a/chrome/browser/android/webapk/webapk_installer.cc b/chrome/browser/android/webapk/webapk_installer.cc
index 37df154bd8a3115e4a5972973c4ac9b6b9766e7b..ba03aeafc78163deac95fea00b5de1510f343d9e 100644
--- a/chrome/browser/android/webapk/webapk_installer.cc
+++ b/chrome/browser/android/webapk/webapk_installer.cc
@@ -52,6 +52,10 @@ const int kWebApkDownloadUrlTimeoutMs = 60000;
 // complete.
 const int kDownloadTimeoutMs = 60000;
 
+const int kWorldReadableFilePermission = base::FILE_PERMISSION_READ_BY_USER |
+                                         base::FILE_PERMISSION_READ_BY_GROUP |
+                                         base::FILE_PERMISSION_READ_BY_OTHERS;
+
 // Returns the scope from |info| if it is specified. Otherwise, returns the
 // default scope.
 GURL GetScope(const ShortcutInfo& info) {
@@ -128,6 +132,38 @@ GURL GetServerUrlForUpdate(const GURL& server_url,
               kDefaultWebApkServerUrlResponseType);
 }
 
+// Creates a directory depending on the type of the task, and set permissions.
+// It also creates any parent directory along the path if doesn't exist,
+// and sets permissions as well.
+// The previously downloaded APKs are deleted in order to clean up unused cached
+// data.
+base::FilePath CreateSubDirAndSetPermissionsInBackground(
+    const base::StringPiece& output_dir_name,
+    const std::string& package_name) {
+  base::FilePath output_root_dir;
+  base::android::GetCacheDirectory(&output_root_dir);
+  base::FilePath webapk_dir = output_root_dir.AppendASCII("webapks");
+  // Creating different downloaded directory for install/update cases is
+  // to prevent deleting the APK which is still in use when an install and an
+  // update happen at the same time. However, it doesn't help the cases of when
+  // mutiple installs (or multiple updates) happen at the same time.
+  base::FilePath output_dir = webapk_dir.AppendASCII(output_dir_name);
+  int posix_permissions = kWorldReadableFilePermission |
+                          base::FILE_PERMISSION_WRITE_BY_USER |
+                          base::FILE_PERMISSION_EXECUTE_BY_USER |
+                          base::FILE_PERMISSION_EXECUTE_BY_OTHERS;
+  if (base::PathExists(output_dir))
+    base::DeleteFile(output_dir, true);
+
+  // Creates the directory to download and sets permissions.
+  if (!base::CreateDirectory(output_dir) ||
+      !base::SetPosixFilePermissions(webapk_dir, posix_permissions) ||
+      !base::SetPosixFilePermissions(output_dir, posix_permissions))
+    return base::FilePath();

[dominickn, 2016/09/28 02:15:03]

Minor nit/question: is it appropriate to clean up output_dir and webapk_dir here
if either of the permission setting calls fails? Not really sure if that's
necessary/appropriate, so I'm not going to block on it. Might be worth following
up though.

[Xi Han, 2016/09/28 02:47:54]

Good point. I am not sure in which cases the setting permissions would fail, but
it is not impossible. The good thing is these code is only temporary and will
not be used once the installation goes through Play.  Anyway, I will keep this
in mind:)

+
+  return output_dir;
+}
+
 }  // anonymous namespace
 
 WebApkInstaller::WebApkInstaller(const ShortcutInfo& shortcut_info,
@@ -348,12 +384,23 @@ void WebApkInstaller::SendRequest(std::unique_ptr<webapk::WebApk> request_proto,
 
 void WebApkInstaller::OnGotWebApkDownloadUrl(const GURL& download_url,
                                              const std::string& package_name) {
-  base::FilePath output_dir;
-  base::android::GetCacheDirectory(&output_dir);
   webapk_package_ = package_name;
-  // TODO(pkotwicz): Download WebAPKs into WebAPK-specific subdirectory
-  // directory.
-  // TODO(pkotwicz): Figure out when downloaded WebAPK should be deleted.
+
+  base::PostTaskAndReplyWithResult(
+      GetBackgroundTaskRunner().get(), FROM_HERE,
+      base::Bind(&CreateSubDirAndSetPermissionsInBackground,
+                 task_type_ == WebApkInstaller::INSTALL ? "install" : "update",
+                 package_name),
+      base::Bind(&WebApkInstaller::OnCreatedSubDirAndSetPermissions,
+                 weak_ptr_factory_.GetWeakPtr(), download_url));
+}
+
+void WebApkInstaller::OnCreatedSubDirAndSetPermissions(
+    const GURL& download_url, const base::FilePath& output_dir) {
+  if (output_dir.empty()) {
+    OnFailure();
+    return;
+  }
 
   timer_.Start(
       FROM_HERE, base::TimeDelta::FromMilliseconds(download_timeout_ms_),
@@ -375,10 +422,9 @@ void WebApkInstaller::OnWebApkDownloaded(const base::FilePath& file_path,
     return;
   }
 
-  int posix_permissions = base::FILE_PERMISSION_READ_BY_USER |
+  int posix_permissions = kWorldReadableFilePermission |
                           base::FILE_PERMISSION_WRITE_BY_USER |
-                          base::FILE_PERMISSION_READ_BY_GROUP |
-                          base::FILE_PERMISSION_READ_BY_OTHERS;
+                          base::FILE_PERMISSION_EXECUTE_BY_USER;
   base::PostTaskAndReplyWithResult(
       GetBackgroundTaskRunner().get(), FROM_HERE,
       base::Bind(&base::SetPosixFilePermissions, file_path, posix_permissions),