Add truncate and cancel for FileWriter; write and tests will come in later CL...

webkit/fileapi/file_system_operation.h

Index: webkit/fileapi/file_system_operation.h
===================================================================
--- webkit/fileapi/file_system_operation.h	(revision 61078)
+++ webkit/fileapi/file_system_operation.h	(working copy)
@@ -61,8 +61,7 @@
 
   void Remove(const FilePath& path);
 
-  void Write(
-      const FilePath& path, const GURL& blob_url, int64 offset);
+  void Write(const FilePath& path, const GURL& blob_url, int64 offset);
 
   void Truncate(const FilePath& path, int64 length);
 
@@ -70,9 +69,10 @@
                  const base::Time& last_access_time,
                  const base::Time& last_modified_time);
 
-  // Used to attempt to cancel the current operation.  This currently does
-  // nothing for any operation other than Write().
-  void Cancel();
+  // Try to cancel the current operation [we support cancelling write or
+  // truncate only].  Report failure for the current operation, then tell the
+  // passed-in operation to report success.
+  void Cancel(FileSystemOperation* cancel_operation);
 
  protected:
   // Proxy for calling file_util_proxy methods.
@@ -114,9 +114,28 @@
 
   base::ScopedCallbackFactory<FileSystemOperation> callback_factory_;
 
+  FileSystemOperation* cancel_operation_;
+
 #ifndef NDEBUG
+  enum OperationType {
+    kOperationNone,
+    kOperationCreateFile,
+    kOperationCreateDirectory,
+    kOperationCopy,
+    kOperationMove,
+    kOperationDirectoryExists,
+    kOperationFileExists,
+    kOperationGetMetadata,
+    kOperationReadDirectory,
+    kOperationRemove,
+    kOperationWrite,
+    kOperationTruncate,
+    kOperationTouchFile,
+    kOperationCancel,
+  };
+
   // A flag to make sure we call operation only once per instance.
-  bool operation_pending_;
+  OperationType pending_operation_;
 #endif
 
   DISALLOW_COPY_AND_ASSIGN(FileSystemOperation);