Revert of Consolidate attachment URL construction.

sync/internal_api/attachments/attachment_downloader_impl.cc

Index: sync/internal_api/attachments/attachment_downloader_impl.cc
diff --git a/sync/internal_api/attachments/attachment_downloader_impl.cc b/sync/internal_api/attachments/attachment_downloader_impl.cc
index 740c4fa03fe62c38e12f720aa4c9471430935dca..18c49d86e74182e564dcc43de1d933f46f283f96 100644
--- a/sync/internal_api/attachments/attachment_downloader_impl.cc
+++ b/sync/internal_api/attachments/attachment_downloader_impl.cc
@@ -9,7 +9,6 @@
 #include "net/base/load_flags.h"
 #include "net/http/http_status_code.h"
 #include "net/url_request/url_fetcher.h"
-#include "sync/internal_api/public/attachments/attachment_uploader_impl.h"
 #include "sync/protocol/sync.pb.h"
 #include "url/gurl.h"
 
@@ -36,7 +35,7 @@
 }
 
 AttachmentDownloaderImpl::AttachmentDownloaderImpl(
-    const GURL& sync_service_url,
+    const std::string& url_prefix,
     const scoped_refptr<net::URLRequestContextGetter>&
         url_request_context_getter,
     const std::string& account_id,
@@ -44,13 +43,14 @@
     scoped_ptr<OAuth2TokenServiceRequest::TokenServiceProvider>
         token_service_provider)
     : OAuth2TokenService::Consumer("attachment-downloader-impl"),
-      sync_service_url_(sync_service_url),
+      url_prefix_(url_prefix),
       url_request_context_getter_(url_request_context_getter),
       account_id_(account_id),
       oauth2_scopes_(scopes),
       token_service_provider_(token_service_provider.Pass()) {
   DCHECK(token_service_provider_);
   DCHECK(url_request_context_getter_);
+  DCHECK(!url_prefix_.empty());
 }
 
 AttachmentDownloaderImpl::~AttachmentDownloaderImpl() {
@@ -61,8 +61,7 @@
     const DownloadCallback& callback) {
   DCHECK(CalledOnValidThread());
 
-  AttachmentUrl url = AttachmentUploaderImpl::GetURLForAttachmentId(
-                          sync_service_url_, attachment_id).spec();
+  AttachmentUrl url = GetAttachmentUrl(attachment_id);
 
   StateMap::iterator iter = state_map_.find(url);
   if (iter == state_map_.end()) {
@@ -150,6 +149,11 @@
   }
   ReportResult(download_state, result, attachment_data);
   state_map_.erase(iter);
+}
+
+AttachmentDownloaderImpl::AttachmentUrl
+AttachmentDownloaderImpl::GetAttachmentUrl(const AttachmentId& attachment_id) {
+  return url_prefix_ + attachment_id.GetProto().unique_id();
 }
 
 scoped_ptr<net::URLFetcher> AttachmentDownloaderImpl::CreateFetcher(