Add mechanism to auto mount file systems in response to a URL request.

chrome/browser/media_galleries/fileapi/media_file_system_backend.h

Index: chrome/browser/media_galleries/fileapi/media_file_system_backend.h
diff --git a/chrome/browser/media_galleries/fileapi/media_file_system_backend.h b/chrome/browser/media_galleries/fileapi/media_file_system_backend.h
index c5f8d99da17f443aa367d53ede20ec8e69273756..7dbfbd139faffe4bd12c12ff47b78b4af240cacb 100644
--- a/chrome/browser/media_galleries/fileapi/media_file_system_backend.h
+++ b/chrome/browser/media_galleries/fileapi/media_file_system_backend.h
@@ -13,6 +13,10 @@ namespace base {
 class SequencedTaskRunner;
 }
 
+namespace net {
+class URLRequest;
+}
+
 class MediaPathFilter;
 
 class DeviceMediaAsyncFileUtil;
@@ -29,6 +33,12 @@ class MediaFileSystemBackend : public fileapi::FileSystemBackend {
   static bool CurrentlyOnMediaTaskRunnerThread();
   static scoped_refptr<base::SequencedTaskRunner> MediaTaskRunner();
 
+  static bool AttemptAutoMountForURLRequest(
+      const net::URLRequest* url_request,
+      const fileapi::FileSystemURL& filesystem_url,
+      const std::string& storage_domain,
+      const base::Callback<void(base::File::Error result)>& callback);
+
   // FileSystemBackend implementation.
   virtual bool CanHandleType(fileapi::FileSystemType type) const OVERRIDE;
   virtual void Initialize(fileapi::FileSystemContext* context) OVERRIDE;