Add a snapshot of flutter/engine/src/build to our sdk

build/android/gyp/util/md5_check.py

Index: build/android/gyp/util/md5_check.py
diff --git a/build/android/gyp/util/md5_check.py b/build/android/gyp/util/md5_check.py
new file mode 100644
index 0000000000000000000000000000000000000000..9f365aa08162c83b22192b675a1a53a5e9acb87f
--- /dev/null
+++ b/build/android/gyp/util/md5_check.py
@@ -0,0 +1,86 @@
+# 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.
+
+import hashlib
+import os
+
+
+def CallAndRecordIfStale(
+    function, record_path=None, input_paths=None, input_strings=None,
+    force=False):
+  """Calls function if the md5sum of the input paths/strings has changed.
+
+  The md5sum of the inputs is compared with the one stored in record_path. If
+  this has changed (or the record doesn't exist), function will be called and
+  the new md5sum will be recorded.
+
+  If force is True, the function will be called regardless of whether the
+  md5sum is out of date.
+  """
+  if not input_paths:
+    input_paths = []
+  if not input_strings:
+    input_strings = []
+  md5_checker = _Md5Checker(
+      record_path=record_path,
+      input_paths=input_paths,
+      input_strings=input_strings)
+  if force or md5_checker.IsStale():
+    function()
+    md5_checker.Write()
+
+
+def _UpdateMd5ForFile(md5, path, block_size=2**16):
+  with open(path, 'rb') as infile:
+    while True:
+      data = infile.read(block_size)
+      if not data:
+        break
+      md5.update(data)
+
+
+def _UpdateMd5ForDirectory(md5, dir_path):
+  for root, _, files in os.walk(dir_path):
+    for f in files:
+      _UpdateMd5ForFile(md5, os.path.join(root, f))
+
+
+def _UpdateMd5ForPath(md5, path):
+  if os.path.isdir(path):
+    _UpdateMd5ForDirectory(md5, path)
+  else:
+    _UpdateMd5ForFile(md5, path)
+
+
+class _Md5Checker(object):
+  def __init__(self, record_path=None, input_paths=None, input_strings=None):
+    if not input_paths:
+      input_paths = []
+    if not input_strings:
+      input_strings = []
+
+    assert record_path.endswith('.stamp'), (
+        'record paths must end in \'.stamp\' so that they are easy to find '
+        'and delete')
+
+    self.record_path = record_path
+
+    md5 = hashlib.md5()
+    for i in sorted(input_paths):
+      _UpdateMd5ForPath(md5, i)
+    for s in input_strings:
+      md5.update(s)
+    self.new_digest = md5.hexdigest()
+
+    self.old_digest = ''
+    if os.path.exists(self.record_path):
+      with open(self.record_path, 'r') as old_record:
+        self.old_digest = old_record.read()
+
+  def IsStale(self):
+    return self.old_digest != self.new_digest
+
+  def Write(self):
+    with open(self.record_path, 'w') as new_record:
+      new_record.write(self.new_digest)