FileSystem mods: Changes to snapshot file creation to remove dependencies on blobs.

content/browser/fileapi/fileapi_message_filter.cc

Index: content/browser/fileapi/fileapi_message_filter.cc
===================================================================
--- content/browser/fileapi/fileapi_message_filter.cc	(revision 182366)
+++ content/browser/fileapi/fileapi_message_filter.cc	(working copy)
@@ -106,6 +106,8 @@
     blob_storage_context_->controller()->RemoveBlob(GURL(*iter));
   }
 
+  in_transit_snapshot_files_.clear();
+
   // Close all files that are previously OpenFile()'ed in this process.
   if (!open_filesystem_urls_.empty()) {
     DLOG(INFO)
@@ -152,6 +154,10 @@
     IPC_MESSAGE_HANDLER(FileSystemHostMsg_NotifyCloseFile, OnNotifyCloseFile)
     IPC_MESSAGE_HANDLER(FileSystemHostMsg_CreateSnapshotFile,
                         OnCreateSnapshotFile)
+    IPC_MESSAGE_HANDLER(FileSystemHostMsg_DidReceiveSnapshotFile,
+                        OnDidReceiveSnapshotFile)
+    IPC_MESSAGE_HANDLER(FileSystemHostMsg_CreateSnapshotFile_Deprecated,
+                        OnCreateSnapshotFile_Deprecated)
     IPC_MESSAGE_HANDLER(FileSystemHostMsg_WillUpdate, OnWillUpdate)
     IPC_MESSAGE_HANDLER(FileSystemHostMsg_DidUpdate, OnDidUpdate)
     IPC_MESSAGE_HANDLER(FileSystemHostMsg_SyncGetPlatformPath,
@@ -539,6 +545,34 @@
 }
 
 void FileAPIMessageFilter::OnCreateSnapshotFile(
+    int request_id, const GURL& path) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
+  FileSystemURL url(context_->CrackURL(path));
+
+  // Make sure if this file can be read by the renderer as this is
+  // called when the renderer is about to create a new File object
+  // (for reading the file).
+  base::PlatformFileError error;
+  if (!HasPermissionsForFile(url, fileapi::kReadFilePermissions, &error)) {
+    Send(new FileSystemMsg_DidFail(request_id, error));
+    return;
+  }
+
+  FileSystemOperation* operation = GetNewOperation(url, request_id);
+  if (!operation)
+    return;
+  operation->CreateSnapshotFile(
+      url,
+      base::Bind(&FileAPIMessageFilter::DidCreateSnapshot,
+                 this, request_id, url));
+}
+
+void FileAPIMessageFilter::OnDidReceiveSnapshotFile(int request_id) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
+  in_transit_snapshot_files_.erase(request_id);
+}
+
+void FileAPIMessageFilter::OnCreateSnapshotFile_Deprecated(
     int request_id, const GURL& blob_url, const GURL& path) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
   FileSystemURL url(context_->CrackURL(path));
@@ -560,7 +594,7 @@
     return;
   operation->CreateSnapshotFile(
       url,
-      base::Bind(&FileAPIMessageFilter::DidCreateSnapshot,
+      base::Bind(&FileAPIMessageFilter::DidCreateSnapshot_Deprecated,
                  this, request_id, register_file_callback));
 }
 
@@ -736,6 +770,57 @@
 
 void FileAPIMessageFilter::DidCreateSnapshot(
     int request_id,
+    const fileapi::FileSystemURL& url,
+    base::PlatformFileError result,
+    const base::PlatformFileInfo& info,
+    const base::FilePath& platform_path,
+    const scoped_refptr<webkit_blob::ShareableFileReference>& snapshot_file) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
+  if (result != base::PLATFORM_FILE_OK) {
+    Send(new FileSystemMsg_DidFail(request_id, result));
+    return;
+  }
+
+  if (!ChildProcessSecurityPolicyImpl::GetInstance()->CanReadFile(
+          process_id_, platform_path)) {
+    // In order for the renderer to be able to read the file, it must be granted
+    // read permission for the file's platform path. By now, it has already been
+    // verified that the renderer has sufficient permissions to read the file.
+    // It is still possible that ChildProcessSecurityPolicyImpl doesn't reflect
+    // that the renderer can read the file's platform path. If this is the case
+    // the renderer should be granted read permission for the file's platform
+    // path. This can happen in the following situations:
+    // - the file comes from sandboxed filesystem. Reading sandboxed files is
+    //   always permitted, but only implicitly.
+    // - the underlying filesystem returned newly created snapshot file.
+    // - the file comes from an external drive filesystem. The renderer has
+    //   already been granted read permission for the file's nominal path, but
+    //   for drive files, platform paths differ from the nominal paths.
+    DCHECK(snapshot_file ||
+           fileapi::SandboxMountPointProvider::CanHandleType(url.type()) ||
+           url.type() == fileapi::kFileSystemTypeDrive);
+    ChildProcessSecurityPolicyImpl::GetInstance()->GrantReadFile(
+        process_id_, platform_path);
+    if (snapshot_file) {
+      // This will revoke all permissions for the file when the last ref
+      // of the file is dropped (assuming it's ok).
+      snapshot_file->AddFinalReleaseCallback(
+          base::Bind(&RevokeFilePermission, process_id_));
+    }
+  }
+
+  if (snapshot_file) {
+    // This ref is held until OnDidReceiveSnapshotFile is called.
+    in_transit_snapshot_files_[request_id] = snapshot_file;
+  }
+
+  // Return the file info and platform_path.
+  Send(new FileSystemMsg_DidCreateSnapshotFile(
+               request_id, info, platform_path));
+}
+
+void FileAPIMessageFilter::DidCreateSnapshot_Deprecated(
+    int request_id,
     const base::Callback<void(const base::FilePath&)>& register_file_callback,
     base::PlatformFileError result,
     const base::PlatformFileInfo& info,