Document and test that image_util.WritePngFile requires path end in 'png'.

content/test/gpu/gpu_tests/cloud_storage_test_base.py

 # Copyright 2013 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Base classes for a test and validator which upload results
 (reference images, error images) to cloud storage."""
 
 import os
 import re
 import tempfile
@@ skipping 125 matching lines @@
     return '%s_v%s_%s.png' % (
       img_name,
       page.revision,
       self._FormatGpuInfo(tab))
 
   def _UploadBitmapToCloudStorage(self, bucket, name, bitmap, public=False):
     # This sequence of steps works on all platforms to write a temporary
     # PNG to disk, following the pattern in bitmap_unittest.py. The key to
     # avoiding PermissionErrors seems to be to not actually try to write to
     # the temporary file object, but to re-open its name for all operations.
-    temp_file = tempfile.NamedTemporaryFile().name
+    temp_file = tempfile.NamedTemporaryFile(suffix='.png').name
     image_util.WritePngFile(bitmap, temp_file)
     cloud_storage.Insert(bucket, name, temp_file, publicly_readable=public)
 
   def _ConditionallyUploadToCloudStorage(self, img_name, page, tab, screenshot):
     """Uploads the screenshot to cloud storage as the reference image
     for this test, unless it already exists. Returns True if the
     upload was actually performed."""
     if not self.options.refimg_cloud_storage_bucket:
       raise Exception('--refimg-cloud-storage-bucket argument is required')
     cloud_name = self._FormatReferenceImageName(img_name, page, tab)
     if not cloud_storage.Exists(self.options.refimg_cloud_storage_bucket,
                                 cloud_name):
       self._UploadBitmapToCloudStorage(self.options.refimg_cloud_storage_bucket,
                                        cloud_name,
                                        screenshot)
       return True
     return False
 
   def _DownloadFromCloudStorage(self, img_name, page, tab):
     """Downloads the reference image for the given test from cloud
     storage, returning it as a Telemetry Bitmap object."""
     # TODO(kbr): there's a race condition between the deletion of the
     # temporary file and gsutil's overwriting it.
     if not self.options.refimg_cloud_storage_bucket:
       raise Exception('--refimg-cloud-storage-bucket argument is required')
-    temp_file = tempfile.NamedTemporaryFile().name
+    temp_file = tempfile.NamedTemporaryFile(suffix='.png').name
     cloud_storage.Get(self.options.refimg_cloud_storage_bucket,
                       self._FormatReferenceImageName(img_name, page, tab),
                       temp_file)
     return image_util.FromPngFile(temp_file)
 
   def _UploadErrorImagesToCloudStorage(self, image_name, screenshot, ref_img):
     """For a failing run, uploads the failing image, reference image (if
     supplied), and diff image (if reference image was supplied) to cloud
     storage. This subsumes the functionality of the
     archive_gpu_pixel_test_results.py script."""
@@ skipping 63 matching lines @@
         default='')
     group.add_option('--test-machine-name',
         help='Name of the test machine. Specifying this argument causes this '
         'script to upload failure images and diffs to cloud storage directly, '
         'instead of relying on the archive_gpu_pixel_test_results.py script.',
         default='')
     group.add_option('--generated-dir',
         help='Overrides the default on-disk location for generated test images '
         '(only used for local testing without a cloud storage account)',
         default=default_generated_data_dir)