Added combined test for Syncable File System to write file and then get that usage gets updated.

chrome/browser/extensions/api/sync_file_system/sync_file_system_apitest.cc

Index: chrome/browser/extensions/api/sync_file_system/sync_file_system_apitest.cc
diff --git a/chrome/browser/extensions/api/sync_file_system/sync_file_system_apitest.cc b/chrome/browser/extensions/api/sync_file_system/sync_file_system_apitest.cc
index 58c6c78ab8518c5ddd3b40a339e12e69794c301b..d3bd83de465ca0041ab197a2479979c7bd55d9ee 100644
--- a/chrome/browser/extensions/api/sync_file_system/sync_file_system_apitest.cc
+++ b/chrome/browser/extensions/api/sync_file_system/sync_file_system_apitest.cc
@@ -57,6 +57,9 @@ class SyncFileSystemApiTest : public ExtensionApiTest {
 
 }  // namespace
 
+// TODO(calvinlo): Add Chrome OS support for syncable file system
+#if !defined(OS_CHROMEOS)
+
 // TODO(benwells): Re-enable this test.
 IN_PROC_BROWSER_TEST_F(SyncFileSystemApiTest, DISABLED_DeleteFileSystem) {
   ASSERT_TRUE(RunPlatformAppTest("sync_file_system/delete_file_system"))
@@ -75,4 +78,12 @@ IN_PROC_BROWSER_TEST_F(SyncFileSystemApiTest, RequestFileSystem) {
       << message_;
 }
 
+IN_PROC_BROWSER_TEST_F(SyncFileSystemApiTest, WriteFileThenGetUsage) {
+  ASSERT_TRUE(RunPlatformAppTest("sync_file_system/write_file_then_get_usage"))
+      << message_;
+}
+
+#endif  // !defined(OS_CHROMEOS)
+
 }  // namespace chrome
+