Add an API to get total size of Drive cache including non-evictable ones.

chrome/browser/chromeos/extensions/file_manager/private_api_file_system.cc

Index: chrome/browser/chromeos/extensions/file_manager/private_api_file_system.cc
diff --git a/chrome/browser/chromeos/extensions/file_manager/private_api_file_system.cc b/chrome/browser/chromeos/extensions/file_manager/private_api_file_system.cc
index 2d0b1831946ad0391559ab6a7212a004cf718b47..c8e57babc6792e15b3ae12e601aae108d69160f6 100644
--- a/chrome/browser/chromeos/extensions/file_manager/private_api_file_system.cc
+++ b/chrome/browser/chromeos/extensions/file_manager/private_api_file_system.cc
@@ -90,7 +90,7 @@ typedef base::Callback<void(const uint64_t* total_size,
 void OnCalculateEvictableCacheSize(const GetSizeStatsCallback& callback,
                                    uint64_t total_size,
                                    uint64_t remaining_size,
-                                   uint64_t evictable_cache_size) {
+                                   int64_t evictable_cache_size) {
   // For calculating real remaining size of Download volume
   // - Adds evictable cache size since the space is available if they are
   //   evicted.