[fsp] Add support for truncating files.

chrome/browser/chromeos/extensions/file_system_provider/file_system_provider_apitest.cc

Index: chrome/browser/chromeos/extensions/file_system_provider/file_system_provider_apitest.cc
diff --git a/chrome/browser/chromeos/extensions/file_system_provider/file_system_provider_apitest.cc b/chrome/browser/chromeos/extensions/file_system_provider/file_system_provider_apitest.cc
index 1fba2ebd1871b728b9d967b1edd6e3cf3f7bfbb5..678e8b4803bc637b70e684befe4808b2afa5fa56 100644
--- a/chrome/browser/chromeos/extensions/file_system_provider/file_system_provider_apitest.cc
+++ b/chrome/browser/chromeos/extensions/file_system_provider/file_system_provider_apitest.cc
@@ -104,4 +104,10 @@ IN_PROC_BROWSER_TEST_F(FileSystemProviderApiTest, MoveEntry) {
       << message_;
 }
 
+IN_PROC_BROWSER_TEST_F(FileSystemProviderApiTest, Truncate) {
+  ASSERT_TRUE(RunPlatformAppTestWithFlags("file_system_provider/truncate",
+                                          kFlagLoadAsComponent))
+      << message_;
+}
+
 }  // namespace extensions