Devtools: gzip the file being served using a temporary file.

This avoids polluting the tree with .gz files when serving from the repo
root.

R=qsr@chromium.org

Review URL: https://codereview.chromium.org/1279543003 .

Cr-Mirrored-From: https://github.com/domokit/mojo
Cr-Mirrored-Commit: 8e13125c1ec8d044f753f9302f72c2d4e5fd33d9

devtoolslib/http_server.py

diff --git a/devtoolslib/http_server.py b/devtoolslib/http_server.py
index a74be0d..482e2db 100644
--- a/devtoolslib/http_server.py
+++ b/devtoolslib/http_server.py
@@ -14,6 +14,7 @@
 import shutil
 import socket
 import threading
+import tempfile
 
 import SimpleHTTPServer
 import SocketServer
@@ -66,10 +67,13 @@
   class RequestHandler(SimpleHTTPServer.SimpleHTTPRequestHandler):
     """Handler for SocketServer.TCPServer that will serve the files from
     local directiories over http.
+
+    A new instance is created for each request.
     """
 
     def __init__(self, *args, **kwargs):
       self.etag = None
+      self.gzipped_file = None
       SimpleHTTPServer.SimpleHTTPRequestHandler.__init__(self, *args, **kwargs)
 
     def get_etag(self):
@@ -147,13 +151,13 @@
                                      normalized_path[len(prefix):])
             if os.path.isfile(candidate):
               if gzipped:
-                gz_result = candidate + '.gz'
-                if (not os.path.isfile(gz_result) or
-                    os.path.getmtime(gz_result) <= os.path.getmtime(candidate)):
-                  with open(candidate, 'rb') as f:
-                    with gzip.open(gz_result, 'wb') as zf:
-                      shutil.copyfileobj(f, zf)
-                return gz_result
+                if not self.gzipped_file:
+                  self.gzipped_file = tempfile.NamedTemporaryFile(delete=False)
+                  with open(candidate, 'rb') as source:
+                    with gzip.GzipFile(fileobj=self.gzipped_file) as target:
+                      shutil.copyfileobj(source, target)
+                  self.gzipped_file.close()
+                return self.gzipped_file.name
               return candidate
           else:
             self.send_response(404)
@@ -174,6 +178,10 @@
       """Override the base class method to disable logging."""
       pass
 
+    def __del__(self):
+      if self.gzipped_file:
+        os.remove(self.gzipped_file.name)
+
   RequestHandler.protocol_version = 'HTTP/1.1'
   return RequestHandler