IDL compiler: Add a hack to work with pydeps

Fixes pydeps settings and makes web_idl module work without
user-side settings of PYTHONPATH.

This hack workarounds an issue that action_with_pydeps and
print_python_deps.py don't provide a chance to set up
PYTHONPATH.

Bug: 839389
Change-Id: I342e3dbd5b6d23a555e3ee253c362e6a82ff6f60
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1751423Reviewed-by: Hitoshi Yoshida <peria@chromium.org>
Commit-Queue: Yuki Shiino <yukishiino@chromium.org>
Cr-Commit-Position: refs/heads/master@{#686409}

third_party/blink/renderer/bindings/BUILD.gn

@@ -99,22 +99,12 @@ collect_idl_files("web_idl_in_modules") {
   output = "${bindings_output_dir}/web_idl_in_modules.pickle"
 }
 
-blink_python_runner("web_idl_database") {
+action_with_pydeps("web_idl_database") {
   script = "${bindings_scripts_dir}/build_web_idl_database.py"
 
   input_data_files = get_target_outputs(":web_idl_in_core") +
                      get_target_outputs(":web_idl_in_modules")
-
-  # List pydeps's content to |pydeps|
-  pydeps_file = "${bindings_scripts_dir}/build_web_idl_database.pydeps"
-  pydeps_dir = get_path_info(pydeps_file, "dir")
-  pydeps_raw = read_file(pydeps_file, "list lines")
-  set_sources_assignment_filter([ "#*" ])
-  sources = pydeps_raw
-  pydeps = sources
-  sources = []
-
-  inputs = input_data_files + rebase_path(pydeps, ".", pydeps_dir)
+  inputs = input_data_files
   output_data_file = "${bindings_output_dir}/web_idl_database.pickle"
   outputs = [
     output_data_file,

third_party/blink/renderer/bindings/scripts/web_idl/__init__.py

@@ -2,11 +2,36 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+import os.path
+import sys
+
+
+# Set up |sys.path| so that this module works without user-side setup of
+# PYTHONPATH assuming Chromium's directory tree structure.
+def _setup_sys_path():
+    expected_path = 'third_party/blink/renderer/bindings/scripts/web_idl/'
+
+    this_dir = os.path.dirname(__file__)
+    root_dir = os.path.join(this_dir, *(['..'] * expected_path.count('/')))
+    sys.path = [
+        # //third_party/ply
+        os.path.join(root_dir, 'third_party'),
+        # //tools/idl_parser
+        os.path.join(root_dir, 'tools'),
+        # //third_party/blink/renderer/build/scripts/blinkbuild
+        os.path.join(this_dir, '..', '..', '..', 'build', 'scripts'),
+    ] + sys.path
+
+
+_setup_sys_path()
+
+
 from .ast_group import AstGroup
 from .composition_parts import Component
 from .database import Database
 from .database_builder import build_database
 
+
 __all__ = [
     "AstGroup",
     "Component",