Refactor PDFium python test utilities.

testing/tools/pngdiffer.py

+#!/usr/bin/env python
+# Copyright 2015 The PDFium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+import os
+import subprocess
+import sys
+
+class PNGDiffer():
+  ACTUAL_TEMPLATE = '.pdf.%d.png'
+  EXPECTED_TEMPLATE = '_expected' + ACTUAL_TEMPLATE
+
+  def __init__(self, finder):
+    self.pdfium_diff_path = finder.ExecutablePath('pdfium_diff')
+
+  def HasDifferences(self, input_filename, source_dir, working_dir):
+    input_root, _ = os.path.splitext(input_filename)
+    actual_path_template = os.path.join(
+        working_dir, input_root + self.ACTUAL_TEMPLATE)
+    expected_path_template = os.path.join(
+        source_dir, input_root + self.EXPECTED_TEMPLATE)
+    i = 0
+    try:
+      while True:
+        actual_path = actual_path_template % i;
+        expected_path = expected_path_template % i;
+        if not os.path.exists(expected_path):
+          if i == 0:
+            print "WARNING: no expected results files for " + input_filename
+          break
+        print "Checking " + actual_path
+        sys.stdout.flush()
+        subprocess.check_call(
+            [self.pdfium_diff_path, expected_path, actual_path])
+        i += 1
+    except subprocess.CalledProcessError as e:
+      print "FAILURE: " + input_filename + "; " + str(e)
+      return True
+    return False