Fix a FileWriter abort race by turning an assert into a soft check.

webkit/fileapi/webfilewriter_base.cc

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "webkit/fileapi/webfilewriter_base.h"
 
 #include "base/logging.h"
 #include "third_party/WebKit/Source/WebKit/chromium/public/WebFileError.h"
 #include "third_party/WebKit/Source/WebKit/chromium/public/WebFileWriterClient.h"
 #include "third_party/WebKit/Source/WebKit/chromium/public/platform/WebURL.h"
@@ skipping 36 matching lines @@
 //   failure [of the write, either from cancel or other reasons] followed by
 //     the result of the cancel.
 // In the write case, there could also be queued up non-terminal DidWrite calls
 // before any of that comes back, but there will always be a terminal write
 // response [success or failure] after them, followed by the cancel result, so
 // we can ignore non-terminal write responses, take the terminal write success
 // or the first failure as the last write response, then know that the next
 // thing to come back is the cancel response.  We only notify the
 // AsyncFileWriterClient when it's all over.
 void WebFileWriterBase::cancel() {
-  DCHECK(kOperationWrite == operation_ || kOperationTruncate == operation_);
+  // Check for the cancel passing the previous operation's return in-flight.
+  if (kOperationWrite != operation_ && kOperationTruncate != operation_)
+    return;
   if (kCancelNotInProgress != cancel_state_)
     return;
   cancel_state_ = kCancelSent;
   DoCancel();
 }
 
 void WebFileWriterBase::DidSucceed() {
   // Write never gets a DidSucceed call, so this is either a cancel or truncate
   // response.
   switch (cancel_state_) {
@@ skipping 68 matching lines @@
 
 void WebFileWriterBase::FinishCancel() {
   DCHECK(kCancelReceivedWriteResponse == cancel_state_);
   DCHECK(kOperationNone != operation_);
   cancel_state_ = kCancelNotInProgress;
   operation_ = kOperationNone;
   client_->didFail(WebKit::WebFileErrorAbort);
 }
 
 }  // namespace fileapi