Evict drive cache with file download from website if necessary.

chrome/browser/chromeos/drive/download_handler.cc

Index: chrome/browser/chromeos/drive/download_handler.cc
diff --git a/chrome/browser/chromeos/drive/download_handler.cc b/chrome/browser/chromeos/drive/download_handler.cc
index 06bc182a95e4b6ab800ca456ebabdf87543cdf75..7f336aa5cf8d628c827f193ecea87d0201623606 100644
--- a/chrome/browser/chromeos/drive/download_handler.cc
+++ b/chrome/browser/chromeos/drive/download_handler.cc
@@ -8,6 +8,7 @@
 #include "base/files/file_util.h"
 #include "base/strings/string_util.h"
 #include "base/supports_user_data.h"
+#include "base/thread_task_runner_handle.h"
 #include "base/threading/sequenced_worker_pool.h"
 #include "chrome/browser/chromeos/drive/drive_integration_service.h"
 #include "chrome/browser/chromeos/drive/file_system_util.h"
@@ -34,6 +35,10 @@ const char kDrivePathKey[] = "DrivePath";
 const char* kGenericMimeTypes[] = {"text/html", "text/plain",
                                    "application/octet-stream"};
 
+const int64 kDefaultRequestSpace = 512 * (1 << 20);  // 512MB

[hashimoto, 2015/10/28 09:06:15]

How was this value chosen? (based on some statistics?)

[yawano, 2015/10/28 09:29:44]

No, this is not based on some statistics.

This value should be
- small as possible since we don't want to evict Drive cache unnecessary.
- large enough as not to be used up until the next FreeDiskSpace (5 secs).

+
+const base::TimeDelta kFreeDiskSpaceDelay = base::TimeDelta::FromSeconds(5);
+
 // User Data stored in DownloadItem for drive path.
 class DriveUserData : public base::SupportsUserData::Data {
  public:
@@ -125,12 +130,15 @@ std::string FilterOutGenericMimeType(const std::string& mime_type) {
   return mime_type;
 }
 
+void IgnoreFreeDiskSpaceIfNeededForCallback(bool /*result*/) {}
+
 }  // namespace
 
 DownloadHandler::DownloadHandler(FileSystemInterface* file_system)
     : file_system_(file_system),
-      weak_ptr_factory_(this) {
-}
+      pending_request_space_(0),
+      free_disk_space_delay_(kFreeDiskSpaceDelay),
+      weak_ptr_factory_(this) {}
 
 DownloadHandler::~DownloadHandler() {
 }
@@ -237,8 +245,44 @@ void DownloadHandler::CheckForFileExistence(
                  callback));
 }
 
+void DownloadHandler::SetFreeDiskSpaceDelayForTesting(
+    const base::TimeDelta& delay) {
+  free_disk_space_delay_ = delay;
+}
+
+// TODO(yawano): support multiple in-progress downloads.

[hashimoto, 2015/10/28 09:06:15]

Why don't you support multiple downloads now?

[yawano, 2015/10/28 09:29:44]

I thought it will make this CL larger. But I think this will be the best timing
to support it. I'll try to implement it in this CL.

+void DownloadHandler::FreeDiskSpaceIfNeeded(const DownloadItem* download,
+                                            bool immediate) {
+  if (download->IsDone())
+    return;
+
+  const int64 total_bytes = download->GetTotalBytes();
+  const int64 request_space = total_bytes == 0

[hashimoto, 2015/10/28 09:06:15]

Please add a comment why we need to handle total_bytes==0 case.

[yawano, 2015/10/29 02:52:43]

Done.

+                                  ? kDefaultRequestSpace

[hashimoto, 2015/10/28 09:06:15]

IIUC, when the download is 99% complete, this can result in requesting needed
bytes + 512MB
Is this really what we want?

[yawano, 2015/10/28 09:29:44]

This value is used when we don't know total bytes of Download. When
content_length is not available, total bytes become 0.

https://code.google.com/p/chromium/codesearch#chromium/src/content/browser/do...

+                                  : total_bytes - download->GetReceivedBytes();
+
+  if (immediate) {
+    file_system_->FreeDiskSpaceIfNeededFor(
+        request_space, base::Bind(&IgnoreFreeDiskSpaceIfNeededForCallback));
+
+    return;
+  }
+
+  const bool post_task = pending_request_space_ == 0;
+  pending_request_space_ = request_space;
+
+  if (post_task) {
+    base::ThreadTaskRunnerHandle::Get()->PostDelayedTask(
+        FROM_HERE, base::Bind(&DownloadHandler::ExecuteFreeDiskSpaceIfNeededFor,
+                              weak_ptr_factory_.GetWeakPtr()),
+        free_disk_space_delay_);
+  }
+}
+
 void DownloadHandler::OnDownloadCreated(DownloadManager* manager,
                                         DownloadItem* download) {
+  FreeDiskSpaceIfNeeded(download, true /* immediate */);
+
   // Remove any persisted Drive DownloadItem. crbug.com/171384
   if (IsPersistedDriveDownload(drive_tmp_download_path_, download)) {
     // Remove download later, since doing it here results in a crash.
@@ -265,6 +309,8 @@ void DownloadHandler::OnDownloadUpdated(
     DownloadManager* manager, DownloadItem* download) {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
 
+  FreeDiskSpaceIfNeeded(download, false /* not immediate */);
+
   // Only accept downloads that have the Drive meta data associated with them.
   DriveUserData* data = GetDriveUserData(download);
   if (!drive_tmp_download_path_.IsParent(download->GetTargetFilePath()) ||
@@ -345,6 +391,14 @@ void DownloadHandler::SetCacheFilePath(void* manager_id,
   data->set_cache_file_path(*cache_file_path);
 }
 
+void DownloadHandler::ExecuteFreeDiskSpaceIfNeededFor() {
+  file_system_->FreeDiskSpaceIfNeededFor(
+      pending_request_space_,
+      base::Bind(&IgnoreFreeDiskSpaceIfNeededForCallback));
+
+  pending_request_space_ = 0;
+}
+
 DownloadManager* DownloadHandler::GetDownloadManager(void* manager_id) {
   if (manager_id == notifier_->GetManager())
     return notifier_->GetManager();