[FileSystem] Expose sandboxed filesystem through new API.

Implements an initial version of getSystemDirectory, with the sandboxed
filesystem being the currently only supported option.

Tbr: jbroman@chromium.org
Bug: 879265
Change-Id: Ic044b00bc650e6e6d8b4aa618dd893ed9c3190ae
Reviewed-on: https://chromium-review.googlesource.com/1197403
Commit-Queue: Marijn Kruisselbrink <mek@chromium.org>
Reviewed-by: Victor Costan <pwnall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#588106}

third_party/blink/renderer/modules/filesystem/file_system_callbacks.cc

@@ -265,6 +265,21 @@ void FileSystemCallbacks::OnDidOpenFileSystemV8Impl::OnSuccess(
   callback_->InvokeAndReportException(nullptr, file_system);
 }
 
+FileSystemCallbacks::OnDidOpenFileSystemPromiseImpl::
+    OnDidOpenFileSystemPromiseImpl(ScriptPromiseResolver* resolver)
+    : resolver_(resolver) {}
+
+void FileSystemCallbacks::OnDidOpenFileSystemPromiseImpl::Trace(
+    Visitor* visitor) {
+  OnDidOpenFileSystemCallback::Trace(visitor);
+  visitor->Trace(resolver_);
+}
+
+void FileSystemCallbacks::OnDidOpenFileSystemPromiseImpl::OnSuccess(
+    DOMFileSystem* file_system) {
+  resolver_->Resolve(file_system->root()->asFileSystemHandle());
+}
+
 std::unique_ptr<AsyncFileSystemCallbacks> FileSystemCallbacks::Create(
     OnDidOpenFileSystemCallback* success_callback,
     ErrorCallbackBase* error_callback,

third_party/blink/renderer/modules/filesystem/file_system_callbacks.h

@@ -249,6 +249,16 @@ class FileSystemCallbacks final : public FileSystemCallbacksBase {
     Member<V8PersistentCallbackInterface<V8FileSystemCallback>> callback_;
   };
 
+  class OnDidOpenFileSystemPromiseImpl : public OnDidOpenFileSystemCallback {
+   public:
+    explicit OnDidOpenFileSystemPromiseImpl(ScriptPromiseResolver*);
+    void Trace(Visitor*) override;
+    void OnSuccess(DOMFileSystem*) override;
+
+   private:
+    Member<ScriptPromiseResolver> resolver_;
+  };
+
   static std::unique_ptr<AsyncFileSystemCallbacks> Create(
       OnDidOpenFileSystemCallback*,
       ErrorCallbackBase*,

third_party/blink/renderer/modules/filesystem/file_system_directory_handle.cc

@@ -7,6 +7,7 @@
 #include "third_party/blink/renderer/bindings/core/v8/script_promise_resolver.h"
 #include "third_party/blink/renderer/modules/filesystem/dom_file_system_base.h"
 #include "third_party/blink/renderer/modules/filesystem/file_system_callbacks.h"
+#include "third_party/blink/renderer/modules/filesystem/local_file_system.h"
 
 namespace blink {
 
@@ -36,4 +37,22 @@ ScriptPromise FileSystemDirectoryHandle::getDirectory(ScriptState* script_state,
   return result;
 }
 
+// static
+ScriptPromise FileSystemDirectoryHandle::getSystemDirectory(
+    ScriptState* script_state,
+    const GetSystemDirectoryOptions& options) {
+  auto* context = ExecutionContext::From(script_state);
+
+  auto* resolver = ScriptPromiseResolver::Create(script_state);
+  ScriptPromise result = resolver->Promise();
+
+  LocalFileSystem::From(*context)->RequestFileSystem(
+      context, mojom::blink::FileSystemType::kTemporary, /*size=*/0,
+      FileSystemCallbacks::Create(
+          new FileSystemCallbacks::OnDidOpenFileSystemPromiseImpl(resolver),
+          new PromiseErrorCallback(resolver), context,
+          mojom::blink::FileSystemType::kTemporary));
+  return result;
+}
+
 }  // namespace blink

third_party/blink/renderer/modules/filesystem/file_system_directory_handle.h

@@ -6,6 +6,7 @@
 #define THIRD_PARTY_BLINK_RENDERER_MODULES_FILESYSTEM_FILE_SYSTEM_DIRECTORY_HANDLE_H_
 
 #include "third_party/blink/renderer/modules/filesystem/file_system_base_handle.h"
+#include "third_party/blink/renderer/modules/filesystem/get_system_directory_options.h"
 
 namespace blink {
 
@@ -18,6 +19,10 @@ class FileSystemDirectoryHandle : public FileSystemBaseHandle {
   bool isDirectory() const override { return true; }
   ScriptPromise getFile(ScriptState*, const String& name);
   ScriptPromise getDirectory(ScriptState*, const String& name);
+
+  static ScriptPromise getSystemDirectory(
+      ScriptState*,
+      const GetSystemDirectoryOptions& options);
 };
 
 }  // namespace blink

third_party/blink/renderer/modules/filesystem/file_system_directory_handle.idl

@@ -9,4 +9,7 @@
     [CallWith=ScriptState] Promise<FileSystemFileHandle> getFile(USVString name);
     [CallWith=ScriptState] Promise<FileSystemDirectoryHandle> getDirectory(USVString name);
     // TODO(mek): Other methods such as getEntries etc.
+
+    [CallWith=ScriptState]
+    static Promise<FileSystemDirectoryHandle> getSystemDirectory(GetSystemDirectoryOptions options);
 };

third_party/blink/renderer/modules/filesystem/get_system_directory_options.idl

+// Copyright 2018 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// https://github.com/WICG/writable-files/blob/master/EXPLAINER.md
+enum SystemDirectoryType {
+  "sandbox"
+};
+
+dictionary GetSystemDirectoryOptions {
+  required SystemDirectoryType type;
+};

third_party/blink/renderer/modules/modules_idl_files.gni

@@ -518,6 +518,7 @@ modules_dictionary_idl_files =
           "encryptedmedia/media_key_system_media_capability.idl",
           "eventsource/event_source_init.idl",
           "filesystem/file_system_flags.idl",
+          "filesystem/get_system_directory_options.idl",
           "gamepad/gamepad_effect_parameters.idl",
           "gamepad/gamepad_event_init.idl",
           "geolocation/position_options.idl",