[style_var_gen] Add generation source info and license header to output.

Bug: 1018654
Change-Id: Idec68bbbcf642f7048d06490de765d423218a61c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2217511Reviewed-by: Giovanni Ortuño Urquidi <ortuno@chromium.org>
Reviewed-by: calamity <calamity@chromium.org>
Commit-Queue: calamity <calamity@chromium.org>
Cr-Commit-Position: refs/heads/master@{#772507}

tools/style_variable_generator/base_generator.py

@@ -54,6 +54,7 @@ class BaseGenerator:
 
     def __init__(self):
         self.out_file_path = None
+        self.in_files = []
         self._mode_variables = dict()
         # The mode that colors will fallback to when not specified in a
         # non-default mode. An error will be raised if a color in any mode is
@@ -72,6 +73,7 @@ class BaseGenerator:
                     self._mode_variables[mode].AddColor(name, value_obj[mode])
 
     def AddJSONFileToModel(self, path):
+        self.in_files.append(path)
         with open(path, 'r') as f:
             # TODO(calamity): Add allow_duplicate_keys=False once pyjson5 is
             # rolled.

tools/style_variable_generator/colors_test_expected.css

+/* Copyright 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. */
+
+/* This file is generated from:
+ *  colors_test.json5
+ */
+
 html:not(body) {
   --google-grey-900-rgb: 32, 33, 36;
   --google-grey-900: rgb(var(--google-grey-900-rgb));

tools/style_variable_generator/colors_test_expected.h

@@ -2,6 +2,9 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// This file is generated from:
+//   colors_test.json5
+
 #ifndef TOOLS_STYLE_VARIABLE_GENERATOR_COLORS_TEST_EXPECTED_H_
 #define TOOLS_STYLE_VARIABLE_GENERATOR_COLORS_TEST_EXPECTED_H_
 

tools/style_variable_generator/css_generator.py

@@ -29,6 +29,7 @@ class CSSStyleGenerator(BaseGenerator):
     def GetGlobals(self):
         return {
             'css_color_from_rgb_var': self._CssColorFromRGBVar,
+            'in_files': self.in_files,
         }
 
     def _ToVarName(self, var_name):

tools/style_variable_generator/css_generator.tmpl

+/* Copyright 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. */
+
+/* This file is generated from:
+{%- for path in in_files %}
+ *  {{path}}
+{%-  endfor %}
+ */
+
 {#
 The :not(body) adds extra selector specificity so that these colors 'win'
 against paper-styles/color.html.

tools/style_variable_generator/style_variable_generator.gni

@@ -60,7 +60,6 @@ template("style_variable_generator") {
              ]
     out_file = "$target_gen_dir/${original_target_name}.h"
     outputs = [ out_file ]
-
     args = [
              "--generator=Views",
              "--out-file",

tools/style_variable_generator/views_generator.py

@@ -30,6 +30,7 @@ class ViewsStyleGenerator(BaseGenerator):
             'Modes': Modes,
             'out_file_path': None,
             'namespace_name': None,
+            'in_files': self.in_files,
         }
         if self.out_file_path:
             globals['out_file_path'] = self.out_file_path

tools/style_variable_generator/views_generator_h.tmpl

@@ -6,6 +6,11 @@
         out_file_path|upper|replace("/","_")|replace(".","_")|
             replace("-", "_")) %}
 
+// This file is generated from:
+{%- for path in in_files %}
+//   {{path}}
+{%-  endfor %}
+
 #ifndef {{header_guard}}
 #define {{header_guard}}