Clean up ARC file system unit tests.

components/arc/test/fake_file_system_instance.cc

Index: components/arc/test/fake_file_system_instance.cc
diff --git a/components/arc/test/fake_file_system_instance.cc b/components/arc/test/fake_file_system_instance.cc
index a0a0aca33a31f367c5ebfe1b89565a64c568eced..0bc2284a120467b74bf2eba438aad6e17334039c 100644
--- a/components/arc/test/fake_file_system_instance.cc
+++ b/components/arc/test/fake_file_system_instance.cc
@@ -4,44 +4,148 @@
 
 #include "components/arc/test/fake_file_system_instance.h"
 
+#include <string.h>
+#include <unistd.h>
+
 #include "base/bind.h"
+#include "base/files/file.h"
+#include "base/files/file_path.h"
+#include "base/files/file_util.h"
+#include "base/files/scoped_file.h"
 #include "base/location.h"
+#include "base/logging.h"
 #include "base/optional.h"
 #include "base/threading/thread_task_runner_handle.h"
-#include "mojo/public/cpp/system/handle.h"
+#include "mojo/edk/embedder/embedder.h"
 
 namespace arc {
 
-FakeFileSystemInstance::FakeFileSystemInstance() = default;
+namespace {
+
+base::ScopedFD CreateRegularFileDescriptor(const char* content,
+                                           const base::FilePath& temp_dir) {
+  base::FilePath path;
+  CHECK(base::CreateTemporaryFileInDir(temp_dir, &path));

[hidehiko, 2017/01/26 07:24:20]

Could you return an error, instead of crash? You can ASSERT_TRUE() in the set
up.

cf) the last item of
https://chromium.googlesource.com/chromium/src/+/master/styleguide/c++/c++.md...

Ditto for below.

[Shuhei Takahashi, 2017/01/27 09:55:10]

As we discussed offline, please let me use DCHECK() for the cases where it makes
sense to crash in unit tests (e.g. obvious errors in setting test expectations,
I/O errors and thread checker). I'll keep in mind to use EXPECT/ASSERT wherever
it makes sense to catch such errors in unit tests.

[hidehiko, 2017/01/27 15:50:00]

Sounds reasonable to me.

+  CHECK_EQ(static_cast<int>(strlen(content)),
+           base::WriteFile(path, content, strlen(content)));
+  base::File file(path, base::File::FLAG_OPEN | base::File::FLAG_READ);
+  CHECK(file.IsValid());
+  return base::ScopedFD(file.TakePlatformFile());
+}
+
+base::ScopedFD CreateStreamFileDescriptor(const char* content) {
+  int fds[2];
+  CHECK_EQ(0, pipe(fds));
+  base::ScopedFD fd_read(fds[0]);
+  base::ScopedFD fd_write(fds[1]);
+  CHECK(base::WriteFileDescriptor(fd_write.get(), content, strlen(content)));
+  return fd_read;
+}
+
+mojom::DocumentPtr MakeDocument(
+    const FakeFileSystemInstance::DocumentSpec& spec) {
+  mojom::DocumentPtr document = mojom::Document::New();
+  document->document_id = spec.document_id;
+  document->display_name = spec.display_name;
+  document->mime_type = spec.mime_type;
+  document->size = spec.size;
+  document->last_modified = spec.last_modified;
+  return document;
+}
+
+}  // namespace
+
+FakeFileSystemInstance::FakeFileSystemInstance() {
+  CHECK(temp_dir_.CreateUniqueTempDir());
+}
 
 FakeFileSystemInstance::~FakeFileSystemInstance() = default;
 
-void FakeFileSystemInstance::GetChildDocuments(
-    const std::string& authority,
-    const std::string& document_id,
-    const GetChildDocumentsCallback& callback) {
-  base::ThreadTaskRunnerHandle::Get()->PostTask(
-      FROM_HERE, base::Bind(callback, base::nullopt));
+void FakeFileSystemInstance::AddFile(const FileSpec& spec) {
+  CHECK_EQ(0u, files_.count(std::string(spec.url)));
+  files_[std::string(spec.url)] = spec;
 }
 
-void FakeFileSystemInstance::GetDocument(const std::string& authority,
-                                         const std::string& document_id,
-                                         const GetDocumentCallback& callback) {
-  base::ThreadTaskRunnerHandle::Get()->PostTask(
-      FROM_HERE, base::Bind(callback, base::Passed(mojom::DocumentPtr())));
+void FakeFileSystemInstance::AddDocument(const DocumentSpec& spec) {
+  DocumentKey key(spec.authority, spec.document_id);
+  CHECK_EQ(0u, documents_.count(key));
+  documents_[key] = spec;
+  child_documents_[key];  // Allocate a vector.
+  if (spec.parent_document_id) {
+    DocumentKey parent_key(spec.authority, spec.parent_document_id);
+    CHECK_EQ(1u, documents_.count(parent_key));
+    child_documents_[parent_key].push_back(key);
+  }
 }
 
 void FakeFileSystemInstance::GetFileSize(const std::string& url,
                                          const GetFileSizeCallback& callback) {
-  base::ThreadTaskRunnerHandle::Get()->PostTask(FROM_HERE,
-                                                base::Bind(callback, -1));
+  auto iter = files_.find(url);
+  if (iter == files_.end()) {
+    base::ThreadTaskRunnerHandle::Get()->PostTask(FROM_HERE,
+                                                  base::Bind(callback, -1));
+    return;
+  }
+  const FileSpec& spec = iter->second;
+  base::ThreadTaskRunnerHandle::Get()->PostTask(
+      FROM_HERE, base::Bind(callback, strlen(spec.content)));
 }
 
 void FakeFileSystemInstance::OpenFileToRead(
     const std::string& url,
     const OpenFileToReadCallback& callback) {
+  auto iter = files_.find(url);
+  if (iter == files_.end()) {
+    base::ThreadTaskRunnerHandle::Get()->PostTask(
+        FROM_HERE, base::Bind(callback, base::Passed(mojo::ScopedHandle())));
+    return;
+  }
+  const FileSpec& spec = iter->second;
+  base::ScopedFD fd = spec.stream ? CreateStreamFileDescriptor(spec.content)
+                                  : CreateRegularFileDescriptor(
+                                        spec.content, temp_dir_.GetPath());
+  mojo::edk::ScopedPlatformHandle platform_handle(
+      mojo::edk::PlatformHandle(fd.release()));
+  MojoHandle wrapped_handle;
+  CHECK_EQ(MOJO_RESULT_OK, mojo::edk::CreatePlatformHandleWrapper(
+                               std::move(platform_handle), &wrapped_handle));
+  base::ThreadTaskRunnerHandle::Get()->PostTask(
+      FROM_HERE, base::Bind(callback, base::Passed(mojo::ScopedHandle(
+                                          mojo::Handle(wrapped_handle)))));
+}
+
+void FakeFileSystemInstance::GetDocument(const std::string& authority,
+                                         const std::string& document_id,
+                                         const GetDocumentCallback& callback) {
+  auto iter = documents_.find(DocumentKey(authority, document_id));
+  if (iter == documents_.end()) {
+    base::ThreadTaskRunnerHandle::Get()->PostTask(
+        FROM_HERE, base::Bind(callback, base::Passed(mojom::DocumentPtr())));
+    return;
+  }
+  base::ThreadTaskRunnerHandle::Get()->PostTask(
+      FROM_HERE,
+      base::Bind(callback, base::Passed(MakeDocument(iter->second))));
+}
+
+void FakeFileSystemInstance::GetChildDocuments(
+    const std::string& authority,
+    const std::string& parent_document_id,
+    const GetChildDocumentsCallback& callback) {
+  auto iter = child_documents_.find(DocumentKey(authority, parent_document_id));
+  if (iter == child_documents_.end()) {
+    base::ThreadTaskRunnerHandle::Get()->PostTask(
+        FROM_HERE, base::Bind(callback, base::nullopt));
+    return;
+  }
+  std::vector<mojom::DocumentPtr> children;
+  for (const auto& child_key : iter->second) {
+    children.emplace_back(MakeDocument(documents_[child_key]));
+  }
   base::ThreadTaskRunnerHandle::Get()->PostTask(
-      FROM_HERE, base::Bind(callback, base::Passed(mojo::ScopedHandle())));
+      FROM_HERE,
+      base::Bind(callback,
+                 base::Passed(base::make_optional(std::move(children)))));
 }
 
 void FakeFileSystemInstance::RequestMediaScan(