Add cef_api_hash.h generated by the translator tool (see issue #2596)

This splits out the API hashes from the cef_version.h file which is generated at
build time. Changes to the cef_api_hash.h file are committed to the repo and
represent potentially breaking API changes. This commit history will be used to
calculate the version number.

tools/make_api_hash_header.py

@@ -0,0 +1,77 @@
+# Copyright (c) 2019 The Chromium Embedded Framework Authors. All rights
+# reserved. Use of this source code is governed by a BSD-style license that
+# can be found in the LICENSE file.
+
+from cef_api_hash import cef_api_hash
+from cef_parser import *
+from file_util import *
+
+
+def make_api_hash_header(cpp_header_dir):
+  # calculate api hashes
+  api_hash_calculator = cef_api_hash(cpp_header_dir, verbose=False)
+  api_hash = api_hash_calculator.calculate()
+
+  result = get_copyright(full=True) + \
+"""#ifndef CEF_INCLUDE_API_HASH_H_
+#define CEF_INCLUDE_API_HASH_H_
+
+#include "include/internal/cef_export.h"
+
+// The API hash is created by analyzing CEF header files for C API type
+// definitions. The hash value will change when header files are modified in a
+// way that may cause binary incompatibility with other builds. The universal
+// hash value will change if any platform is affected whereas the platform hash
+// values will change only if that particular platform is affected.
+#define CEF_API_HASH_UNIVERSAL "$UNIVERSAL$"
+#if defined(OS_WIN)
+#define CEF_API_HASH_PLATFORM "$WINDOWS$"
+#elif defined(OS_MACOSX)
+#define CEF_API_HASH_PLATFORM "$MACOSX$"
+#elif defined(OS_LINUX)
+#define CEF_API_HASH_PLATFORM "$LINUX$"
+#endif
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+///
+// Returns CEF API hashes for the libcef library. The returned string is owned
+// by the library and should not be freed. The |entry| parameter describes which
+// hash value will be returned:
+// 0 - CEF_API_HASH_PLATFORM
+// 1 - CEF_API_HASH_UNIVERSAL
+// 2 - CEF_COMMIT_HASH (from cef_version.h)
+///
+CEF_EXPORT const char* cef_api_hash(int entry);
+
+#ifdef __cplusplus
+}
+#endif
+#endif  // CEF_INCLUDE_API_HASH_H_
+"""
+
+  # Substitute hash values for placeholders.
+  for platform, value in api_hash.iteritems():
+    result = result.replace('$%s$' % platform.upper(), value)
+
+  return result
+
+
+def write_api_hash_header(header, cpp_header_dir):
+  newcontents = make_api_hash_header(cpp_header_dir)
+  return (header, newcontents)
+
+
+# Test the module.
+if __name__ == "__main__":
+  import sys
+
+  # Verify that the correct number of command-line arguments are provided.
+  if len(sys.argv) < 2:
+    sys.stderr.write('Usage: ' + sys.argv[0] + ' <cppheaderdir>')
+    sys.exit()
+
+  # Dump the result to stdout.
+  sys.stdout.write(make_api_hash_header(sys.argv[1]))