mediaview: Implement ArcDocumentsProviderBackendDelegate.

chrome/browser/chromeos/arc/fileapi/arc_documents_provider_backend_delegate.cc

Index: chrome/browser/chromeos/arc/fileapi/arc_documents_provider_backend_delegate.cc
diff --git a/chrome/browser/chromeos/arc/fileapi/arc_documents_provider_backend_delegate.cc b/chrome/browser/chromeos/arc/fileapi/arc_documents_provider_backend_delegate.cc
index 6572b4c6050203801703db1a3bd0d5399d0cbcd8..f4b09093f1bcc1ac4be2a351927d05afae76b794 100644
--- a/chrome/browser/chromeos/arc/fileapi/arc_documents_provider_backend_delegate.cc
+++ b/chrome/browser/chromeos/arc/fileapi/arc_documents_provider_backend_delegate.cc
@@ -7,6 +7,9 @@
 #include <utility>
 
 #include "base/logging.h"
+#include "base/memory/ptr_util.h"
+#include "chrome/browser/chromeos/arc/fileapi/arc_documents_provider_file_stream_reader.h"
+#include "chrome/browser/chromeos/arc/fileapi/arc_documents_provider_root.h"
 #include "content/public/browser/browser_thread.h"
 #include "storage/browser/fileapi/file_stream_reader.h"
 #include "storage/browser/fileapi/file_stream_writer.h"
@@ -17,7 +20,7 @@ using content::BrowserThread;
 namespace arc {
 
 ArcDocumentsProviderBackendDelegate::ArcDocumentsProviderBackendDelegate()
-    : async_file_util_(&roots_) {}
+    : async_file_util_(&roots_), weak_ptr_factory_(this) {}
 
 ArcDocumentsProviderBackendDelegate::~ArcDocumentsProviderBackendDelegate() {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
@@ -37,8 +40,20 @@ ArcDocumentsProviderBackendDelegate::CreateFileStreamReader(
     const base::Time& expected_modification_time,
     storage::FileSystemContext* context) {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
-  NOTIMPLEMENTED();  // TODO(crbug.com/671511): Implement this function.
-  return nullptr;
+
+  auto reader = base::MakeUnique<ArcDocumentsProviderFileStreamReader>(offset);
+
+  base::FilePath path;
+  ArcDocumentsProviderRoot* root = roots_.ParseAndLookup(url, &path);
+  if (!root) {
+    reader->SetContentUrl(GURL());
+    return std::move(reader);
+  }
+
+  root->ResolveToContentUrl(
+      path, base::Bind(&ArcDocumentsProviderFileStreamReader::SetContentUrl,
+                       reader->GetWeakPtr()));
+  return std::move(reader);
 }
 
 std::unique_ptr<storage::FileStreamWriter>
@@ -62,7 +77,7 @@ void ArcDocumentsProviderBackendDelegate::GetRedirectURLForContents(
     const storage::FileSystemURL& url,
     const storage::URLCallback& callback) {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
-  NOTIMPLEMENTED();  // TODO(crbug.com/671511): Implement this function.
+  NOTREACHED();  // Never called by chromeos::FileSystemBackend.
   callback.Run(GURL());
 }