Add request header on gdata operation for testing ETag match.

chrome/browser/google_apis/drive_service_interface.h

Index: chrome/browser/google_apis/drive_service_interface.h
diff --git a/chrome/browser/google_apis/drive_service_interface.h b/chrome/browser/google_apis/drive_service_interface.h
index 412a9295e35355b7a33229ef93411298c2637e4a..3d484fa4f95c1e79880beee038ff05c986d3fa78 100644
--- a/chrome/browser/google_apis/drive_service_interface.h
+++ b/chrome/browser/google_apis/drive_service_interface.h
@@ -148,6 +148,7 @@ class DriveServiceInterface {
   // Deletes a document identified by its 'self' |url| and |etag|.
   // Upon completion, invokes |callback| with results on the calling thread.
   virtual void DeleteDocument(const GURL& document_url,
+                              const std::string& etag,
                               const gdata::EntryActionCallback& callback) = 0;
 
   // Downloads a document identified by its |content_url| in a given |format|.
@@ -157,6 +158,7 @@ class DriveServiceInterface {
       const FilePath& local_cache_path,
       const GURL& content_url,
       DocumentExportFormat format,
+      const std::string& etag,
       const gdata::DownloadActionCallback& callback) = 0;
 
   // Makes a copy of a document identified by its |resource_id|.
@@ -212,6 +214,7 @@ class DriveServiceInterface {
       const FilePath& virtual_path,
       const FilePath& local_cache_path,
       const GURL& content_url,
+      const std::string& etag,
       const gdata::DownloadActionCallback& download_action_callback,
       const gdata::GetContentCallback& get_content_callback) = 0;