luci-py/isolateserver.py: Add archive support when downloading.

client/tests/isolateserver_test.py

Index: client/tests/isolateserver_test.py
diff --git a/client/tests/isolateserver_test.py b/client/tests/isolateserver_test.py
index 12c8f1c62cf0b305a077ee3a64cda74e16dc1fdf..ef60ec4de2c34ed5517b8d6c7341269a55d39c2b 100755
--- a/client/tests/isolateserver_test.py
+++ b/client/tests/isolateserver_test.py
@@ -724,7 +724,7 @@ class IsolateServerStorageSmokeTest(unittest.TestCase):
     # Ensure fetched same data as was pushed.
     self.assertEqual(
         [i.buffer for i in items],
-        [cache.read(i.digest) for i in items])
+        [cache.getfileobj(i.digest).read() for i in items])
 
   def test_push_and_fetch(self):
     self.run_push_and_fetch_test('default')
@@ -841,9 +841,9 @@ class IsolateServerDownloadTest(TestCase):
   def test_download_isolated(self):
     # Test downloading an isolated tree.
     actual = {}
-    def file_write_mock(key, generator):
-      actual[key] = ''.join(generator)
-    self.mock(isolateserver, 'file_write', file_write_mock)
+    def putfile_mock(srcfileobj, dstpath, file_mode=None):
+      actual[dstpath] = srcfileobj.read()
+    self.mock(isolateserver, 'putfile', putfile_mock)
     self.mock(os, 'makedirs', lambda _: None)
     server = 'http://example.com'
     files = {