Unmounts volumes before writing to a drive.

chrome/browser/extensions/api/image_writer_private/operation_manager.cc

Index: chrome/browser/extensions/api/image_writer_private/operation_manager.cc
diff --git a/chrome/browser/extensions/api/image_writer_private/operation_manager.cc b/chrome/browser/extensions/api/image_writer_private/operation_manager.cc
index f87f8ccbf7fe82ab6dc9a5ecd980cf9e588a0257..c9d524e77f9b63e7ffbec79bd46cf39644f0dc5d 100644
--- a/chrome/browser/extensions/api/image_writer_private/operation_manager.cc
+++ b/chrome/browser/extensions/api/image_writer_private/operation_manager.cc
@@ -66,7 +66,12 @@ void OperationManager::StartWriteFromUrl(
     const Operation::StartWriteCallback& callback) {
   OperationMap::iterator existing_operation = operations_.find(extension_id);
 
+#if defined(OS_CHROMEOS)
+  // Chrome OS can only support a single operation at a time.
+  if (operations_.size() > 0) {
+#else
   if (existing_operation != operations_.end()) {
+#endif
     return callback.Run(false, error::kOperationAlreadyInProgress);
   }
 
@@ -91,7 +96,12 @@ void OperationManager::StartWriteFromFile(
     const Operation::StartWriteCallback& callback) {
   OperationMap::iterator existing_operation = operations_.find(extension_id);
 
+#if defined(OS_CHROMEOS)
+  // Chrome OS can only support a single operation at a time.
+  if (operations_.size() > 0) {
+#else
   if (existing_operation != operations_.end()) {
+#endif
     return callback.Run(false, error::kOperationAlreadyInProgress);
   }