[Files app]: Add scripts for JS modules conversion

Command:
ui/file_manager/base/tools/modules.sh [1] [2]
[1] build directory (e.g. out/Release)
[2] path of JS file to convert (relative to chromium/src)

What does the script do:
1. Update BUILD.gn to enable conversion of JS file.
2. Add exports.
3. Run closure compiler.
4. Parse closure compiler output to retrieve unknown types/variables/functions.
6. Parse these dependencies to find relevant exported types/variables/functions.
7. When found, update BUILD.gn and JS file.

Made sure that:
The script doesn't add any irrelevant import/export.
No duplicate lines are added.

Steps 3 to 7 are ran until the closure compiler output
'X error(s), Y warning(s), Z% typed' doesn't change. The closure compiler
is ran at least 3 times (except if no imports are found), sometimes more.

Bug: 1133186
Change-Id: I1528c8187bc1476d6add1bcb14a0d4fd1b64a4fe
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2550328
Commit-Queue: Jeremie Boulic <jboulic@chromium.org>
Reviewed-by: Luciano Pacheco <lucmult@chromium.org>
Cr-Commit-Position: refs/heads/master@{#834181}

ui/file_manager/base/tools/modules.sh

+#!/bin/bash
+#
+# Copyright (c) 2020 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.
+
+# Command usage:
+# ui/file_manager/base/tools/modules.sh out/Release ui/file_manager/
+#   file_manager/foreground/js/list_thumbnail_loader.js
+# ui/file_manager/base/tools/modules.sh out/Release ui/file_manager/
+#   file_manager/common/js/importer_common.js
+# ui/file_manager/base/tools/modules.sh out/Release ui/file_manager/
+#   file_manager/foreground/js/list_thumbnail_loader_unittest.js
+
+# Input: js file to convert.
+build_dir=$1;
+file_path=$2;
+dir=`dirname $file_path`;
+compiler_output="$build_dir/gen/ui/file_manager/base/tools/compiler_output.txt";
+
+# Create containing directory of `compiler_output` if doesn't exist.
+mkdir -p `dirname $compiler_output`;
+
+# Process files with Python.
+ui/file_manager/base/tools/modules.py $file_path 'generate';
+
+# Parse closure compiler output and update files until the message 'X error(s),
+# Y warning(s), Z% typed' doesn't change.
+prev_output=""
+new_output="."
+while [[ $prev_output != $new_output ]]; do
+  prev_output=$new_output;
+
+  # Run closure compiler and save output.
+  ninja -C $build_dir $dir:closure_compile 2>&1 | tee $compiler_output;
+
+  # Parse closure compiler output.
+  ui/file_manager/base/tools/modules.py $file_path 'parse' $compiler_output;
+
+  # Get number of errors from modules.txt.
+  new_output=$(cat $compiler_output | grep 'error(s)' );
+done;
+
+# Format files.
+git cl format --js;
+
+if [[ $new_output == "" ]]; then
+  echo "No closure compiler error found"
+else
+  echo "Final state: " $new_output;
+fi;