Revert 282900 "Revert 282890 "[fsp] Add an option for mounting i..."

Unable to reproduce locally even on a Debug build. Reverting the revert and
monitoring carefully.

> Revert 282890 "[fsp] Add an option for mounting in R/W mode."
> 
> > [fsp] Add an option for mounting in R/W mode.
> > 
> > Files app fetches information whether a volume is read only or R/W from
> > file_manager::VolumeManager, which used to always have the isReadOnly option
> > set to true for any provided file system.
> > 
> > However, since R/W operations are now under development, we should be able to
> > mark a volume as R/W.
> > 
> > In order to achieve that, a "writable" option has been added to the File System
> > Provider API mount() call. The argument is by default false, so file systems
> > are by default read only.
> > 
> > TEST=unit_test, browser_tests: *FileSystemProvider*Writable*
> > BUG=391362
> > 
> > Review URL: https://codereview.chromium.org/372163006
> 
> TBR=mtomasz@chromium.org
> 
> Review URL: https://codereview.chromium.org/391613002

TBR=mtomasz@chromium.org

Review URL: https://codereview.chromium.org/389243002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@282908 0039d316-1c4b-4281-b951-d872f2087c98

chrome/browser/chromeos/extensions/file_system_provider/file_system_provider_api.cc

@@ -52,7 +52,8 @@ bool FileSystemProviderMountFunction::RunSync() {
   // TODO(mtomasz): Pass more detailed errors, rather than just a bool.
   if (!service->MountFileSystem(extension_id(),
                                 params->options.file_system_id,
-                                params->options.display_name)) {
+                                params->options.display_name,
+                                params->options.writable)) {
     base::ListValue* result = new base::ListValue();
     result->Append(CreateError(kSecurityErrorName, kMountFailedErrorMessage));
     SetResult(result);

chrome/browser/chromeos/file_manager/volume_manager.cc

@@ -220,7 +220,7 @@ VolumeInfo CreateProvidedFileSystemVolumeInfo(
   volume_info.mount_path = file_system_info.mount_path();
   volume_info.mount_condition = chromeos::disks::MOUNT_CONDITION_NONE;
   volume_info.is_parent = true;
-  volume_info.is_read_only = true;
+  volume_info.is_read_only = !file_system_info.writable();
   volume_info.volume_id = GenerateVolumeId(volume_info);
   return volume_info;
 }

chrome/browser/chromeos/file_system_provider/fileapi/file_stream_reader_unittest.cc

@@ -96,8 +96,10 @@ class FileSystemProviderFileStreamReader : public testing::Test {
     service->SetFileSystemFactoryForTesting(
         base::Bind(&FakeProvidedFileSystem::Create));
 
-    const bool result = service->MountFileSystem(
-        kExtensionId, kFileSystemId, "Testing File System");
+    const bool result = service->MountFileSystem(kExtensionId,
+                                                 kFileSystemId,
+                                                 "Testing File System",
+                                                 false /* writable */);
     ASSERT_TRUE(result);
     const ProvidedFileSystemInfo& file_system_info =
         service->GetProvidedFileSystem(kExtensionId, kFileSystemId)

chrome/browser/chromeos/file_system_provider/fileapi/provider_async_file_util_unittest.cc

@@ -141,8 +141,10 @@ class FileSystemProviderProviderAsyncFileUtilTest : public testing::Test {
     service->SetFileSystemFactoryForTesting(
         base::Bind(&FakeProvidedFileSystem::Create));
 
-    const bool result = service->MountFileSystem(
-        kExtensionId, kFileSystemId, "Testing File System");
+    const bool result = service->MountFileSystem(kExtensionId,
+                                                 kFileSystemId,
+                                                 "Testing File System",
+                                                 false /* writable */);
     ASSERT_TRUE(result);
     const ProvidedFileSystemInfo& file_system_info =
         service->GetProvidedFileSystem(kExtensionId, kFileSystemId)

chrome/browser/chromeos/file_system_provider/mount_path_util_unittest.cc

@@ -127,7 +127,7 @@ TEST_F(FileSystemProviderMountPathUtilTest, IsFileSystemProviderLocalPath) {
 
 TEST_F(FileSystemProviderMountPathUtilTest, Parser) {
   const bool result = file_system_provider_service_->MountFileSystem(
-      kExtensionId, kFileSystemId, kDisplayName);
+      kExtensionId, kFileSystemId, kDisplayName, false /* writable */);
   ASSERT_TRUE(result);
   const ProvidedFileSystemInfo file_system_info =
       file_system_provider_service_->GetProvidedFileSystem(kExtensionId,
@@ -151,7 +151,7 @@ TEST_F(FileSystemProviderMountPathUtilTest, Parser) {
 
 TEST_F(FileSystemProviderMountPathUtilTest, Parser_RootPath) {
   const bool result = file_system_provider_service_->MountFileSystem(
-      kExtensionId, kFileSystemId, kDisplayName);
+      kExtensionId, kFileSystemId, kDisplayName, false /* writable */);
   ASSERT_TRUE(result);
   const ProvidedFileSystemInfo file_system_info =
       file_system_provider_service_->GetProvidedFileSystem(kExtensionId,
@@ -177,6 +177,7 @@ TEST_F(FileSystemProviderMountPathUtilTest, Parser_WrongUrl) {
       kExtensionId,
       kFileSystemId,
       kDisplayName,
+      false /* writable */,
       GetMountPath(profile_, kExtensionId, kFileSystemId));
 
   const base::FilePath kFilePath = base::FilePath::FromUTF8Unsafe("/hello");
@@ -192,7 +193,7 @@ TEST_F(FileSystemProviderMountPathUtilTest, Parser_WrongUrl) {
 
 TEST_F(FileSystemProviderMountPathUtilTest, Parser_IsolatedURL) {
   const bool result = file_system_provider_service_->MountFileSystem(
-      kExtensionId, kFileSystemId, kDisplayName);
+      kExtensionId, kFileSystemId, kDisplayName, false /* writable */);
   ASSERT_TRUE(result);
   const ProvidedFileSystemInfo file_system_info =
       file_system_provider_service_->GetProvidedFileSystem(kExtensionId,
@@ -238,7 +239,7 @@ TEST_F(FileSystemProviderMountPathUtilTest, Parser_IsolatedURL) {
 
 TEST_F(FileSystemProviderMountPathUtilTest, LocalPathParser) {
   const bool result = file_system_provider_service_->MountFileSystem(
-      kExtensionId, kFileSystemId, kDisplayName);
+      kExtensionId, kFileSystemId, kDisplayName, false /* writable */);
   ASSERT_TRUE(result);
   const ProvidedFileSystemInfo file_system_info =
       file_system_provider_service_->GetProvidedFileSystem(kExtensionId,
@@ -262,7 +263,7 @@ TEST_F(FileSystemProviderMountPathUtilTest, LocalPathParser) {
 
 TEST_F(FileSystemProviderMountPathUtilTest, LocalPathParser_RootPath) {
   const bool result = file_system_provider_service_->MountFileSystem(
-      kExtensionId, kFileSystemId, kDisplayName);
+      kExtensionId, kFileSystemId, kDisplayName, false /* writable */);
   ASSERT_TRUE(result);
   const ProvidedFileSystemInfo file_system_info =
       file_system_provider_service_->GetProvidedFileSystem(kExtensionId,

chrome/browser/chromeos/file_system_provider/operations/close_file_unittest.cc

@@ -40,6 +40,7 @@ class FileSystemProviderOperationsCloseFileTest : public testing::Test {
         ProvidedFileSystemInfo(kExtensionId,
                                kFileSystemId,
                                "" /* display_name */,
+                               false /* writable */,
                                base::FilePath() /* mount_path */);
   }
 

chrome/browser/chromeos/file_system_provider/operations/create_directory_unittest.cc

@@ -40,6 +40,7 @@ class FileSystemProviderOperationsCreateDirectoryTest : public testing::Test {
         ProvidedFileSystemInfo(kExtensionId,
                                kFileSystemId,
                                "" /* file_system_name */,
+                               true /* writable */,
                                base::FilePath() /* mount_path */);
   }
 

chrome/browser/chromeos/file_system_provider/operations/delete_entry_unittest.cc

@@ -40,6 +40,7 @@ class FileSystemProviderOperationsDeleteEntryTest : public testing::Test {
         ProvidedFileSystemInfo(kExtensionId,
                                kFileSystemId,
                                "" /* file_system_name */,
+                               false /* writable */,
                                base::FilePath() /* mount_path */);
   }
 

chrome/browser/chromeos/file_system_provider/operations/get_metadata_unittest.cc

@@ -77,6 +77,7 @@ class FileSystemProviderOperationsGetMetadataTest : public testing::Test {
         ProvidedFileSystemInfo(kExtensionId,
                                kFileSystemId,
                                "" /* display_name */,
+                               false /* writable */,
                                base::FilePath() /* mount_path */);
   }
 

chrome/browser/chromeos/file_system_provider/operations/open_file_unittest.cc

@@ -76,6 +76,7 @@ class FileSystemProviderOperationsOpenFileTest : public testing::Test {
         ProvidedFileSystemInfo(kExtensionId,
                                kFileSystemId,
                                "" /* display_name */,
+                               false /* writable */,
                                base::FilePath() /* mount_path */);
   }
 

chrome/browser/chromeos/file_system_provider/operations/read_directory_unittest.cc

@@ -84,6 +84,7 @@ class FileSystemProviderOperationsReadDirectoryTest : public testing::Test {
         ProvidedFileSystemInfo(kExtensionId,
                                kFileSystemId,
                                "" /* display_name */,
+                               false /* writable */,
                                base::FilePath() /* mount_path */);
   }
 

chrome/browser/chromeos/file_system_provider/operations/read_file_unittest.cc

@@ -81,6 +81,7 @@ class FileSystemProviderOperationsReadFileTest : public testing::Test {
         ProvidedFileSystemInfo(kExtensionId,
                                kFileSystemId,
                                "" /* display_name */,
+                               false /* writable */,
                                base::FilePath() /* mount_path */);
     io_buffer_ = make_scoped_refptr(new net::IOBuffer(kOffset + kLength));
   }

chrome/browser/chromeos/file_system_provider/operations/unmount_unittest.cc

@@ -38,6 +38,7 @@ class FileSystemProviderOperationsUnmountTest : public testing::Test {
         ProvidedFileSystemInfo(kExtensionId,
                                kFileSystemId,
                                "" /* display_name */,
+                               false /* writable */,
                                base::FilePath() /* mount_path */);
   }
 

chrome/browser/chromeos/file_system_provider/provided_file_system_info.cc

@@ -13,10 +13,12 @@ ProvidedFileSystemInfo::ProvidedFileSystemInfo(
     const std::string& extension_id,
     const std::string& file_system_id,
     const std::string& display_name,
+    bool writable,
     const base::FilePath& mount_path)
     : extension_id_(extension_id),
       file_system_id_(file_system_id),
       display_name_(display_name),
+      writable_(writable),
       mount_path_(mount_path) {
 }
 

chrome/browser/chromeos/file_system_provider/provided_file_system_info.h

@@ -19,6 +19,7 @@ class ProvidedFileSystemInfo {
   ProvidedFileSystemInfo(const std::string& extension_id,
                          const std::string& file_system_id,
                          const std::string& display_name,
+                         const bool writable,
                          const base::FilePath& mount_path);
 
   ~ProvidedFileSystemInfo();
@@ -26,6 +27,7 @@ class ProvidedFileSystemInfo {
   const std::string& extension_id() const { return extension_id_; }
   const std::string& file_system_id() const { return file_system_id_; }
   const std::string& display_name() const { return display_name_; }
+  bool writable() const { return writable_; }
   const base::FilePath& mount_path() const { return mount_path_; }
 
  private:
@@ -38,6 +40,9 @@ class ProvidedFileSystemInfo {
   // Name of the file system, can be rendered in the UI.
   std::string display_name_;
 
+  // Whether the file system is writable or just read-only.
+  bool writable_;
+
   // Mount path of the underlying file system.
   base::FilePath mount_path_;
 };

chrome/browser/chromeos/file_system_provider/service.cc

@@ -39,6 +39,7 @@ ProvidedFileSystemInterface* CreateProvidedFileSystem(
 
 const char kPrefKeyFileSystemId[] = "file-system-id";
 const char kPrefKeyDisplayName[] = "display-name";
+const char kPrefKeyWritable[] = "writable";
 
 void RegisterProfilePrefs(user_prefs::PrefRegistrySyncable* registry) {
   registry->RegisterDictionaryPref(
@@ -101,7 +102,8 @@ void Service::SetFileSystemFactoryForTesting(
 
 bool Service::MountFileSystem(const std::string& extension_id,
                               const std::string& file_system_id,
-                              const std::string& display_name) {
+                              const std::string& display_name,
+                              bool writable) {
   DCHECK(thread_checker_.CalledOnValidThread());
 
   // If already exists a file system provided by the same extension with this
@@ -149,11 +151,12 @@ bool Service::MountFileSystem(const std::string& extension_id,
   // Store the file system descriptor. Use the mount point name as the file
   // system provider file system id.
   // Examples:
-  //   file_system_id = 41
-  //   mount_point_name =  b33f1337-41-5aa5
-  //   mount_path = /provided/b33f1337-41-5aa5
+  //   file_system_id = hello_world
+  //   mount_point_name =  b33f1337-hello_world-5aa5
+  //   writable = false
+  //   mount_path = /provided/b33f1337-hello_world-5aa5
   ProvidedFileSystemInfo file_system_info(
-      extension_id, file_system_id, display_name, mount_path);
+      extension_id, file_system_id, display_name, writable, mount_path);
 
   ProvidedFileSystemInterface* file_system =
       file_system_factory_.Run(profile_, file_system_info);
@@ -331,6 +334,8 @@ void Service::RememberFileSystem(
                                              file_system_info.file_system_id());
   file_system->SetStringWithoutPathExpansion(kPrefKeyDisplayName,
                                              file_system_info.display_name());
+  file_system->SetBooleanWithoutPathExpansion(kPrefKeyWritable,
+                                              file_system_info.writable());
 
   PrefService* const pref_service = profile_->GetPrefs();
   DCHECK(pref_service);
@@ -397,21 +402,23 @@ void Service::RestoreFileSystems(const std::string& extension_id) {
 
     std::string file_system_id;
     std::string display_name;
-    if (file_system_value->GetAsDictionary(&file_system)) {
-      file_system->GetStringWithoutPathExpansion(kPrefKeyFileSystemId,
-                                                 &file_system_id);
-      file_system->GetStringWithoutPathExpansion(kPrefKeyDisplayName,
-                                                 &display_name);
-    }
-
-    if (file_system_id.empty() || display_name.empty()) {
+    bool writable;
+
+    if (!file_system_value->GetAsDictionary(&file_system) ||
+        !file_system->GetStringWithoutPathExpansion(kPrefKeyFileSystemId,
+                                                    &file_system_id) ||
+        !file_system->GetStringWithoutPathExpansion(kPrefKeyDisplayName,
+                                                    &display_name) ||
+        !file_system->GetBooleanWithoutPathExpansion(kPrefKeyWritable,
+                                                     &writable) ||
+        file_system_id.empty() || display_name.empty()) {
       LOG(ERROR)
           << "Malformed provided file system information in preferences.";
       continue;
     }
 
     const bool result =
-        MountFileSystem(extension_id, file_system_id, display_name);
+        MountFileSystem(extension_id, file_system_id, display_name, writable);
     if (!result) {
       LOG(ERROR) << "Failed to restore a provided file system from "
                  << "preferences: " << extension_id << ", " << file_system_id

chrome/browser/chromeos/file_system_provider/service.h

@@ -39,6 +39,7 @@ namespace file_system_provider {
 // Key names for preferences.
 extern const char kPrefKeyFileSystemId[];
 extern const char kPrefKeyDisplayName[];
+extern const char kPrefKeyWritable[];
 
 class ProvidedFileSystemFactoryInterface;
 class ProvidedFileSystemInfo;
@@ -71,11 +72,14 @@ class Service : public KeyedService,
   void SetFileSystemFactoryForTesting(
       const FileSystemFactoryCallback& factory_callback);
 
-  // Mounts a file system provided by an extension with the |extension_id|.
-  // For success, returns true, otherwise false.
+  // Mounts a file system provided by an extension with the |extension_id|. If
+  // |writable| is set to true, then the file system is mounted in a R/W mode.
+  // Otherwise, only read-only operations are supported. For success, returns
+  // true, otherwise false.
   bool MountFileSystem(const std::string& extension_id,
                        const std::string& file_system_id,
-                       const std::string& display_name);
+                       const std::string& display_name,
+                       bool writable);
 
   // Unmounts a file system with the specified |file_system_id| for the
   // |extension_id|. For success returns true, otherwise false.

chrome/browser/chromeos/file_system_provider/service_unittest.cc

@@ -100,7 +100,8 @@ scoped_refptr<extensions::Extension> createFakeExtension(
 void RememberFakeFileSystem(TestingProfile* profile,
                             const std::string& extension_id,
                             const std::string& file_system_id,
-                            const std::string& display_name) {
+                            const std::string& display_name,
+                            bool writable) {
   TestingPrefServiceSyncable* const pref_service =
       profile->GetTestingPrefService();
   ASSERT_TRUE(pref_service);
@@ -111,6 +112,7 @@ void RememberFakeFileSystem(TestingProfile* profile,
   file_system->SetStringWithoutPathExpansion(kPrefKeyFileSystemId,
                                              kFileSystemId);
   file_system->SetStringWithoutPathExpansion(kPrefKeyDisplayName, kDisplayName);
+  file_system->SetBooleanWithoutPathExpansion(kPrefKeyWritable, writable);
   file_systems->SetWithoutPathExpansion(kFileSystemId, file_system);
   extensions.SetWithoutPathExpansion(kExtensionId, file_systems);
 
@@ -150,8 +152,8 @@ TEST_F(FileSystemProviderServiceTest, MountFileSystem) {
   LoggingObserver observer;
   service_->AddObserver(&observer);
 
-  EXPECT_TRUE(
-      service_->MountFileSystem(kExtensionId, kFileSystemId, kDisplayName));
+  EXPECT_TRUE(service_->MountFileSystem(
+      kExtensionId, kFileSystemId, kDisplayName, false /* writable */));
 
   ASSERT_EQ(1u, observer.mounts.size());
   EXPECT_EQ(kExtensionId, observer.mounts[0].file_system_info().extension_id());
@@ -162,6 +164,7 @@ TEST_F(FileSystemProviderServiceTest, MountFileSystem) {
   EXPECT_EQ(expected_mount_path.AsUTF8Unsafe(),
             observer.mounts[0].file_system_info().mount_path().AsUTF8Unsafe());
   EXPECT_EQ(kDisplayName, observer.mounts[0].file_system_info().display_name());
+  EXPECT_FALSE(observer.mounts[0].file_system_info().writable());
   EXPECT_EQ(base::File::FILE_OK, observer.mounts[0].error());
   ASSERT_EQ(0u, observer.unmounts.size());
 
@@ -172,14 +175,31 @@ TEST_F(FileSystemProviderServiceTest, MountFileSystem) {
   service_->RemoveObserver(&observer);
 }
 
+TEST_F(FileSystemProviderServiceTest, MountFileSystem_Writable) {
+  LoggingObserver observer;
+  service_->AddObserver(&observer);
+
+  EXPECT_TRUE(service_->MountFileSystem(
+      kExtensionId, kFileSystemId, kDisplayName, true /* writable */));
+
+  ASSERT_EQ(1u, observer.mounts.size());
+  EXPECT_TRUE(observer.mounts[0].file_system_info().writable());
+  ASSERT_EQ(0u, observer.unmounts.size());
+  std::vector<ProvidedFileSystemInfo> file_system_info_list =
+      service_->GetProvidedFileSystemInfoList();
+  ASSERT_EQ(1u, file_system_info_list.size());
+
+  service_->RemoveObserver(&observer);
+}
+
 TEST_F(FileSystemProviderServiceTest, MountFileSystem_UniqueIds) {
   LoggingObserver observer;
   service_->AddObserver(&observer);
 
-  EXPECT_TRUE(
-      service_->MountFileSystem(kExtensionId, kFileSystemId, kDisplayName));
-  EXPECT_FALSE(
-      service_->MountFileSystem(kExtensionId, kFileSystemId, kDisplayName));
+  EXPECT_TRUE(service_->MountFileSystem(
+      kExtensionId, kFileSystemId, kDisplayName, false /* writable */));
+  EXPECT_FALSE(service_->MountFileSystem(
+      kExtensionId, kFileSystemId, kDisplayName, false /* writable */));
 
   ASSERT_EQ(2u, observer.mounts.size());
   EXPECT_EQ(base::File::FILE_OK, observer.mounts[0].error());
@@ -200,14 +220,14 @@ TEST_F(FileSystemProviderServiceTest, MountFileSystem_StressTest) {
   for (size_t i = 0; i < kMaxFileSystems; ++i) {
     const std::string file_system_id =
         std::string("test-") + base::IntToString(i);
-    EXPECT_TRUE(
-        service_->MountFileSystem(kExtensionId, file_system_id, kDisplayName));
+    EXPECT_TRUE(service_->MountFileSystem(
+        kExtensionId, file_system_id, kDisplayName, false /* writable */));
   }
   ASSERT_EQ(kMaxFileSystems, observer.mounts.size());
 
   // The next file system is out of limit, and registering it should fail.
-  EXPECT_FALSE(
-      service_->MountFileSystem(kExtensionId, kFileSystemId, kDisplayName));
+  EXPECT_FALSE(service_->MountFileSystem(
+      kExtensionId, kFileSystemId, kDisplayName, false /* writable */));
 
   ASSERT_EQ(kMaxFileSystems + 1, observer.mounts.size());
   EXPECT_EQ(base::File::FILE_ERROR_TOO_MANY_OPENED,
@@ -224,8 +244,8 @@ TEST_F(FileSystemProviderServiceTest, UnmountFileSystem) {
   LoggingObserver observer;
   service_->AddObserver(&observer);
 
-  EXPECT_TRUE(
-      service_->MountFileSystem(kExtensionId, kFileSystemId, kDisplayName));
+  EXPECT_TRUE(service_->MountFileSystem(
+      kExtensionId, kFileSystemId, kDisplayName, false /* writable */));
   ASSERT_EQ(1u, observer.mounts.size());
 
   EXPECT_TRUE(service_->UnmountFileSystem(
@@ -249,8 +269,8 @@ TEST_F(FileSystemProviderServiceTest, UnmountFileSystem_OnExtensionUnload) {
   LoggingObserver observer;
   service_->AddObserver(&observer);
 
-  EXPECT_TRUE(
-      service_->MountFileSystem(kExtensionId, kFileSystemId, kDisplayName));
+  EXPECT_TRUE(service_->MountFileSystem(
+      kExtensionId, kFileSystemId, kDisplayName, false /* writable */));
   ASSERT_EQ(1u, observer.mounts.size());
 
   // Directly call the observer's method.
@@ -280,8 +300,8 @@ TEST_F(FileSystemProviderServiceTest, UnmountFileSystem_WrongExtensionId) {
 
   const std::string kWrongExtensionId = "helloworldhelloworldhelloworldhe";
 
-  EXPECT_TRUE(
-      service_->MountFileSystem(kExtensionId, kFileSystemId, kDisplayName));
+  EXPECT_TRUE(service_->MountFileSystem(
+      kExtensionId, kFileSystemId, kDisplayName, false /* writable */));
   ASSERT_EQ(1u, observer.mounts.size());
   ASSERT_EQ(1u, service_->GetProvidedFileSystemInfoList().size());
 
@@ -300,8 +320,11 @@ TEST_F(FileSystemProviderServiceTest, UnmountFileSystem_WrongExtensionId) {
 
 TEST_F(FileSystemProviderServiceTest, RestoreFileSystem_OnExtensionLoad) {
   // Create a fake entry in the preferences.
-  RememberFakeFileSystem(
-      profile_.get(), kExtensionId, kFileSystemId, kDisplayName);
+  RememberFakeFileSystem(profile_.get(),
+                         kExtensionId,
+                         kFileSystemId,
+                         kDisplayName,
+                         true /* writable */);
 
   // Create a new service instance in order to load remembered file systems
   // from preferences.
@@ -324,6 +347,7 @@ TEST_F(FileSystemProviderServiceTest, RestoreFileSystem_OnExtensionLoad) {
   EXPECT_EQ(kExtensionId, observer.mounts[0].file_system_info().extension_id());
   EXPECT_EQ(kFileSystemId,
             observer.mounts[0].file_system_info().file_system_id());
+  EXPECT_TRUE(observer.mounts[0].file_system_info().writable());
 
   std::vector<ProvidedFileSystemInfo> file_system_info_list =
       new_service->GetProvidedFileSystemInfoList();
@@ -336,8 +360,8 @@ TEST_F(FileSystemProviderServiceTest, RememberFileSystem_OnMount) {
   LoggingObserver observer;
   service_->AddObserver(&observer);
 
-  EXPECT_TRUE(
-      service_->MountFileSystem(kExtensionId, kFileSystemId, kDisplayName));
+  EXPECT_TRUE(service_->MountFileSystem(
+      kExtensionId, kFileSystemId, kDisplayName, true /* writable */));
   ASSERT_EQ(1u, observer.mounts.size());
 
   TestingPrefServiceSyncable* const pref_service =
@@ -369,6 +393,11 @@ TEST_F(FileSystemProviderServiceTest, RememberFileSystem_OnMount) {
                                                          &display_name));
   EXPECT_EQ(kDisplayName, display_name);
 
+  bool writable = false;
+  EXPECT_TRUE(
+      file_system->GetBooleanWithoutPathExpansion(kPrefKeyWritable, &writable));
+  EXPECT_TRUE(writable);
+
   service_->RemoveObserver(&observer);
 }
 
@@ -381,8 +410,8 @@ TEST_F(FileSystemProviderServiceTest, RememberFileSystem_OnUnmountOnShutdown) {
   ASSERT_TRUE(pref_service);
 
   {
-    EXPECT_TRUE(
-        service_->MountFileSystem(kExtensionId, kFileSystemId, kDisplayName));
+    EXPECT_TRUE(service_->MountFileSystem(
+        kExtensionId, kFileSystemId, kDisplayName, false /* writable */));
     ASSERT_EQ(1u, observer.mounts.size());
 
     const base::DictionaryValue* extensions =
@@ -421,8 +450,8 @@ TEST_F(FileSystemProviderServiceTest, RememberFileSystem_OnUnmountByUser) {
   ASSERT_TRUE(pref_service);
 
   {
-    EXPECT_TRUE(
-        service_->MountFileSystem(kExtensionId, kFileSystemId, kDisplayName));
+    EXPECT_TRUE(service_->MountFileSystem(
+        kExtensionId, kFileSystemId, kDisplayName, false /* writable */));
     ASSERT_EQ(1u, observer.mounts.size());
 
     const base::DictionaryValue* extensions =

chrome/common/extensions/api/file_system_provider.idl

@@ -57,6 +57,7 @@ namespace fileSystemProvider {
   dictionary MountOptions {
     DOMString fileSystemId;
     DOMString displayName;
+    [nodoc] boolean? writable;
   };
 
   // Options for the <code>unmount()</code> method.

chrome/test/data/extensions/api_test/file_system_provider/mount/test.js

@@ -34,6 +34,7 @@ chrome.test.runTests([
           onTestSuccess();
         });
   },
+
   // Verifies that mounting fails, when an empty string is provided as an Id
   function emptyFileSystemId() {
     var onTestSuccess = chrome.test.callbackPass();
@@ -59,14 +60,45 @@ chrome.test.runTests([
         {fileSystemId: fileSystemId, displayName: 'caramel-candy.zip'},
         function() {
           chrome.fileBrowserPrivate.getVolumeMetadataList(function(volumeList) {
-            var found = false;
-            volumeList.forEach(function(volumeInfo) {
-              if (volumeInfo.extensionId == chrome.runtime.id &&
-                  volumeInfo.fileSystemId == fileSystemId) {
-                found = true;
+            var volumeInfo;
+            volumeList.forEach(function(inVolumeInfo) {
+              if (inVolumeInfo.extensionId == chrome.runtime.id &&
+                  inVolumeInfo.fileSystemId == fileSystemId) {
+                volumeInfo = inVolumeInfo;
+              }
+            });
+            chrome.test.assertTrue(!!volumeInfo);
+            chrome.test.assertTrue(volumeInfo.isReadOnly);
+            onTestSuccess();
+          });
+        },
+        function(error) {
+          chrome.test.fail();
+        });
+  },
+
+  // Checks whether mounting a file system in writable mode ends up on filling
+  // out the volume info properly.
+  function successfulWritableMount() {
+    var onTestSuccess = chrome.test.callbackPass();
+    var fileSystemId = 'caramel-fudges';
+    chrome.fileSystemProvider.mount(
+        {
+          fileSystemId: fileSystemId,
+          displayName: 'caramel-fudges.zip',
+          writable: true
+        },
+        function() {
+          chrome.fileBrowserPrivate.getVolumeMetadataList(function(volumeList) {
+            var volumeInfo;
+            volumeList.forEach(function(inVolumeInfo) {
+              if (inVolumeInfo.extensionId == chrome.runtime.id &&
+                  inVolumeInfo.fileSystemId == fileSystemId) {
+                volumeInfo = inVolumeInfo;
               }
             });
-            chrome.test.assertTrue(found);
+            chrome.test.assertTrue(!!volumeInfo);
+            chrome.test.assertFalse(volumeInfo.isReadOnly);
             onTestSuccess();
           });
         },
@@ -81,7 +113,7 @@ chrome.test.runTests([
   // security error.
   function stressMountTest() {
     var onTestSuccess = chrome.test.callbackPass();
-    var ALREADY_MOUNTED_FILE_SYSTEMS = 2;  // By previous tests.
+    var ALREADY_MOUNTED_FILE_SYSTEMS = 3;  // By previous tests.
     var MAX_FILE_SYSTEMS = 16;
     var index = 0;
     var tryNextOne = function() {