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..ffe47a8e5dee84d8bbabb5234ba93df25788f728 100644
--- a/chrome/browser/google_apis/drive_service_interface.h
+++ b/chrome/browser/google_apis/drive_service_interface.h
@@ -145,18 +145,22 @@ class DriveServiceInterface {
   // Upon completion, invokes |callback| with results on the calling thread.
   virtual void GetApplicationInfo(const gdata::GetDataCallback& callback) = 0;
 
-  // Deletes a document identified by its 'self' |url| and |etag|.
+  // Deletes a document identified by its 'self' |document_url|.
+  // If |etag| is set, checks if it matches the document before deletion.

[satorux1, 2012/10/17 03:14:27]

If etag does not match, what happens? Please document. I guess the server
returns an error. If so, what error?

   // 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|.
+  // If |etag| is set, checks if it matches the document before downloading.

[satorux1, 2012/10/17 03:14:27]

ditto.

   // Upon completion, invokes |callback| with results on the calling thread.
   virtual void DownloadDocument(
       const FilePath& virtual_path,
       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|.
@@ -202,9 +206,11 @@ class DriveServiceInterface {
                                const FilePath::StringType& directory_name,
                                const gdata::GetDataCallback& callback) = 0;
 
-  // Downloads a file identified by its |content_url|. The downloaded file will
-  // be stored at |local_cache_path| location. Upon completion, invokes
-  // |download_action_callback| with results on the calling thread.
+  // Downloads a file identified by its |content_url|.
+  // If |etag| is set, checks if it matches the file before downloading.

[satorux1, 2012/10/17 03:14:27]

ditto.

+  // The downloaded file will be stored at |local_cache_path| location.
+  // Upon completion, invokes |download_action_callback| with results on the
+  // calling thread.
   // If |get_content_callback| is not empty,
   // URLFetcherDelegate::OnURLFetchDownloadData will be called, which will in
   // turn invoke |get_content_callback| on the calling thread.
@@ -212,6 +218,7 @@ 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;