net: Implement canceling of all async operations in FileStream.

Canceling of async operations allows to not wait for their completion
in FileStream's destructor. Other related changes include:

- Got rid of FileStream::Close() and FileStream::CloseSync() methods because
reuse of FileStream object doesn't make much sense, it should be destroyed
instead.

- Changed FileStream to always acquire ownership of the PlatformFile it was
given. Fixed usages of FileStream where no ownership was assumed, introduced
new helper functions in base/platform_file.h on the way.

- FileStream's destructor now always closes the file. If file was opened with
PLATFORM_FILE_ASYNC then actual closing is done asynchronously, destructor
doesn't wait for that and returns immediately. When file was opened without
PLATFORM_FILE_ASYNC closing is done synchronously and the thread doing that
should be allowed to do IO operations.

- Implementation of FileStream is refactored. FileStream is now just a wrapper
around internal object that does all actual work and that can be easily
orphaned in the destructor to not block on the actual file descriptor closing.
All platform-independent code is extracted into a special file and amount of
platform-dependent code is minimized.


BUG=115067, 112474
TEST=net_unittests

Review URL: https://chromiumcodereview.appspot.com/10701050

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@166091 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 3 insertions, 2 deletions

diff --git a/chrome/browser/sessions/session_backend.cc b/chrome/browser/sessions/session_backend.cc
index 95cc5d1..8540a79 100644
--- a/chrome/browser/sessions/session_backend.cc
+++ b/chrome/browser/sessions/session_backend.cc
@@ -349,9 +349,10 @@ bool SessionBackend::AppendCommandsToFile(net::FileStream* file,
 
 SessionBackend::~SessionBackend() {
   if (current_session_file_.get()) {
-    // Close() performs file IO. crbug.com/112512.
+    // Destructor performs file IO because file is open in sync mode.
+    // crbug.com/112512.
     base::ThreadRestrictions::ScopedAllowIO allow_io;
-    current_session_file_->CloseSync();
+    current_session_file_.reset();
   }
 }