Asynchronously open the temp file used for Pepper StreamToFile, and delete the

temp file once we are done with it.

We observe ResourceHandle::OnRequestClosed as a signal of when we should delete
the temp file.  This corresponds to the WebURLLoader being closed (or
canceled).

This patch also includes some helpers:

base/scoped_callback_factory.h
  This class makes it easy to allocate Callbacks that hold a weak reference
  back to the owning class.  It works just like ScopedRunnableMethodFactory
  but for Callbacks instead of RunnableMethods.

base/platform_file.h
  Added a PassPlatformFile class that is useful for cases where a callback may
  decide not to take ownership of a PlatformFile (as can happen when using
  ScopedCallbackFactory).

chrome/file_system_proxy.{h,cc}
  This class provides static methods for executing file system commands on the
  FILE thread.  It routes callbacks back to the originating thread to deliver
  results (file handles, etc.).  Note: this file declares a few functions that
  are not yet used.  I anticipate that we'll make use of these and add more
  functions here to support the Pepper and OWP FileSystem APIs.

chrome/chrome_thread_relay.{h,cc}
  This class is a helper class for proxying calls over to a background
  ChromeThread and then returning results to the originating ChromeThread.

R=brettw
BUG=49789
TEST=(more to be added in third_party/ppapi/tests)

Review URL: http://codereview.chromium.org/2878062

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@54402 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 38 insertions, 0 deletions

diff --git a/base/platform_file.h b/base/platform_file.h
index 3571e24..43f8511 100644
--- a/base/platform_file.h
+++ b/base/platform_file.h
@@ -54,6 +54,44 @@ PlatformFile CreatePlatformFile(const std::wstring& name,
 // Closes a file handle
 bool ClosePlatformFile(PlatformFile file);
 
+// Use this class to pass ownership of a PlatformFile to a receiver that may or
+// may not want to accept it.  This class does not own the storage for the
+// PlatformFile.
+//
+// EXAMPLE:
+//
+//  void MaybeProcessFile(PassPlatformFile pass_file) {
+//    if (...) {
+//      PlatformFile file = pass_file.ReleaseValue();
+//      // Now, we are responsible for closing |file|.
+//    }
+//  }
+//
+//  void OpenAndMaybeProcessFile(const FilePath& path) {
+//    PlatformFile file = CreatePlatformFile(path, ...);
+//    MaybeProcessFile(PassPlatformFile(&file));
+//    if (file != kInvalidPlatformFileValue)
+//      ClosePlatformFile(file);
+//  }
+//
+class PassPlatformFile {
+ public:
+  explicit PassPlatformFile(PlatformFile* value) : value_(value) {
+  }
+
+  // Called to retrieve the PlatformFile stored in this object.  The caller
+  // gains ownership of the PlatformFile and is now responsible for closing it.
+  // Any subsequent calls to this method will return an invalid PlatformFile.
+  PlatformFile ReleaseValue() {
+    PlatformFile temp = *value_;
+    *value_ = kInvalidPlatformFileValue;
+    return temp;
+  }
+
+ private:
+  PlatformFile* value_;
+};
+
 }  // namespace base
 
 #endif  // BASE_PLATFORM_FILE_H_