Migrate Blink CSS minifier to GRIT

This patch migrates the Blink CSS minifier to GRIT and applies it
whenever GRIT creates a CSS resource. This allows us to minify all
CSS resources in a unified and effortless manner.

As a result, this patch achieves 12k Android binary size reduction:

https://ci.chromium.org/p/chromium/builders/try/android-binary-size/368229

Bug: 1015410
Change-Id: Ief8efe57d26f2e26c3b53523d8c973d1d193d20b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1900259Reviewed-by: Lei Zhang <thestig@chromium.org>
Reviewed-by: Chris Harrelson <chrishtr@chromium.org>
Reviewed-by: Philip Rogers <pdr@chromium.org>
Commit-Queue: Xiaocheng Hu <xiaochengh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#713567}

third_party/blink/public/BUILD.gn

@@ -553,14 +553,6 @@ grit("resources") {
     "grit/blink_resources.h",
     "blink_resources.pak",
   ]
-  grit_flags = [
-    "-E",
-    "blink_core_output_dir=" +
-        rebase_path(blink_core_output_dir, root_build_dir),
-  ]
-  deps = [
-    "//third_party/blink/renderer/core:make_minimized_css",
-  ]
 }
 
 grit("image_resources") {

third_party/blink/public/blink_resources.grd

@@ -8,40 +8,38 @@
   </outputs>
   <release seq="1">
     <includes>
-      <!-- Certain CSS files are processed through minimize_css.py -->
-      <include name="IDR_UASTYLE_HTML_CSS" file="${cwd}/${blink_core_output_dir}/html.css" type="BINDATA" compress="gzip"/>
-      <include name="IDR_UASTYLE_QUIRKS_CSS" file="${cwd}/${blink_core_output_dir}/quirks.css" type="BINDATA" compress="gzip"/>
-      <include name="IDR_UASTYLE_VIEW_SOURCE_CSS" file="${cwd}/${blink_core_output_dir}/view-source.css" type="BINDATA" compress="gzip"/>
-      <include name="IDR_UASTYLE_THEME_CHROMIUM_ANDROID_CSS" file="${cwd}/${blink_core_output_dir}/android.css" type="BINDATA" compress="gzip"/>
-      <include name="IDR_UASTYLE_FULLSCREEN_ANDROID_CSS" file="${cwd}/${blink_core_output_dir}/fullscreenAndroid.css" type="BINDATA" compress="gzip"/>
-      <include name="IDR_UASTYLE_THEME_CHROMIUM_LINUX_CSS" file="${cwd}/${blink_core_output_dir}/linux.css" type="BINDATA" compress="gzip"/>
+      <!-- GRIT minimizes all CSS and Javascript -->
+      <include name="IDR_UASTYLE_HTML_CSS" file="../renderer/core/html/resources/html.css" type="BINDATA" compress="gzip"/>
+      <include name="IDR_UASTYLE_QUIRKS_CSS" file="../renderer/core/html/resources/quirks.css" type="BINDATA" compress="gzip"/>
+      <include name="IDR_UASTYLE_VIEW_SOURCE_CSS" file="../renderer/core/css/view-source.css" type="BINDATA" compress="gzip"/>
+      <include name="IDR_UASTYLE_THEME_CHROMIUM_ANDROID_CSS" file="../renderer/core/html/resources/android.css" type="BINDATA" compress="gzip"/>
+      <include name="IDR_UASTYLE_FULLSCREEN_ANDROID_CSS" file="../renderer/core/css/fullscreenAndroid.css" type="BINDATA" compress="gzip"/>
+      <include name="IDR_UASTYLE_THEME_CHROMIUM_LINUX_CSS" file="../renderer/core/html/resources/linux.css" type="BINDATA" compress="gzip"/>
       <if expr="is_macosx">
         <include name="IDR_UASTYLE_THEME_MAC_CSS" file="../renderer/core/html/resources/mac.css" type="BINDATA" compress="gzip"/>
       </if>
-      <include name="IDR_UASTYLE_THEME_INPUT_MULTIPLE_FIELDS_CSS" file="${cwd}/${blink_core_output_dir}/input_multiple_fields.css" type="BINDATA" compress="gzip"/>
-      <include name="IDR_UASTYLE_THEME_WIN_CSS" file="${cwd}/${blink_core_output_dir}/win.css" type="BINDATA" compress="gzip"/>
-      <include name="IDR_UASTYLE_THEME_WIN_QUIRKS_CSS" file="${cwd}/${blink_core_output_dir}/win_quirks.css" type="BINDATA" compress="gzip"/>
-      <!-- TODO(crbug.com/1015410): Use minimized |controls_refresh.css| with relative urls properly revised -->
+      <include name="IDR_UASTYLE_THEME_INPUT_MULTIPLE_FIELDS_CSS" file="../renderer/core/html/resources/input_multiple_fields.css" type="BINDATA" compress="gzip"/>
+      <include name="IDR_UASTYLE_THEME_WIN_CSS" file="../renderer/core/html/resources/win.css" type="BINDATA" compress="gzip"/>
+      <include name="IDR_UASTYLE_THEME_WIN_QUIRKS_CSS" file="../renderer/core/html/resources/win_quirks.css" type="BINDATA" compress="gzip"/>
       <include name="IDR_UASTYLE_THEME_CONTROLS_REFRESH_CSS" file="../renderer/core/html/resources/controls_refresh.css" flattenhtml="true" type="BINDATA" compress="gzip"/>
-      <include name="IDR_UASTYLE_THEME_FORCED_COLORS_CSS" file="${cwd}/${blink_core_output_dir}/forced_colors.css" type="BINDATA" compress="gzip"/>
-      <include name="IDR_UASTYLE_SVG_CSS" file="${cwd}/${blink_core_output_dir}/svg.css" type="BINDATA" compress="gzip"/>
-      <include name="IDR_UASTYLE_MATHML_CSS" file="${cwd}/${blink_core_output_dir}/mathml.css" type="BINDATA" compress="gzip"/>
-      <include name="IDR_UASTYLE_FULLSCREEN_CSS" file="${cwd}/${blink_core_output_dir}/fullscreen.css" type="BINDATA" compress="gzip"/>
-      <include name="IDR_UASTYLE_XHTMLMP_CSS" file="${cwd}/${blink_core_output_dir}/xhtmlmp.css" type="BINDATA" compress="gzip"/>
-      <include name="IDR_UASTYLE_VIEWPORT_ANDROID_CSS" file="${cwd}/${blink_core_output_dir}/viewportAndroid.css" type="BINDATA" compress="gzip"/>
-      <include name="IDR_UASTYLE_VIEWPORT_TELEVISION_CSS" file="${cwd}/${blink_core_output_dir}/viewportTelevision.css" type="BINDATA" compress="gzip"/>
-
+      <include name="IDR_UASTYLE_THEME_FORCED_COLORS_CSS" file="../renderer/core/html/resources/forced_colors.css" type="BINDATA" compress="gzip"/>
+      <include name="IDR_UASTYLE_SVG_CSS" file="../renderer/core/css/svg.css" type="BINDATA" compress="gzip"/>
+      <include name="IDR_UASTYLE_MATHML_CSS" file="../renderer/core/css/mathml.css" type="BINDATA" compress="gzip"/>
+      <include name="IDR_UASTYLE_FULLSCREEN_CSS" file="../renderer/core/css/fullscreen.css" type="BINDATA" compress="gzip"/>
+      <include name="IDR_UASTYLE_XHTMLMP_CSS" file="../renderer/core/css/xhtmlmp.css" type="BINDATA" compress="gzip"/>
+      <include name="IDR_UASTYLE_VIEWPORT_ANDROID_CSS" file="../renderer/core/css/viewportAndroid.css" type="BINDATA" compress="gzip"/>
+      <include name="IDR_UASTYLE_VIEWPORT_TELEVISION_CSS" file="../renderer/core/css/viewportTelevision.css" type="BINDATA" compress="gzip"/>
       <include name="IDR_INSPECT_TOOL_COMMON_JS" file="../renderer/core/inspector/inspect_tool_common.js" type="BINDATA" compress="gzip"/>
-      <include name="IDR_INSPECT_TOOL_COMMON_CSS" file="${cwd}/${blink_core_output_dir}/inspect_tool_common.css" type="BINDATA" compress="gzip"/>
+      <include name="IDR_INSPECT_TOOL_COMMON_CSS" file="../renderer/core/inspector/inspect_tool_common.css" type="BINDATA" compress="gzip"/>
       <include name="IDR_INSPECT_TOOL_DISTANCES_HTML" file="../renderer/core/inspector/inspect_tool_distances.html" type="BINDATA" compress="gzip"/>
       <include name="IDR_INSPECT_TOOL_HIGHLIGHT_HTML" file="../renderer/core/inspector/inspect_tool_highlight.html" type="BINDATA" compress="gzip"/>
       <include name="IDR_INSPECT_TOOL_PAUSED_HTML" file="../renderer/core/inspector/inspect_tool_paused.html" type="BINDATA" compress="gzip"/>
       <include name="IDR_INSPECT_TOOL_VIEWPORT_SIZE_HTML" file="../renderer/core/inspector/inspect_tool_viewport_size.html" type="BINDATA" compress="gzip"/>
       <include name="IDR_INSPECT_TOOL_SCREENSHOT_HTML" file="../renderer/core/inspector/inspect_tool_screenshot.html" type="BINDATA" compress="gzip"/>
-      <include name="IDR_DOCUMENTXMLTREEVIEWER_CSS" file="${cwd}/${blink_core_output_dir}/DocumentXMLTreeViewer.css" type="BINDATA" compress="gzip"/>
+      <include name="IDR_DOCUMENTXMLTREEVIEWER_CSS" file="../renderer/core/xml/DocumentXMLTreeViewer.css" type="BINDATA" compress="gzip"/>
       <include name="IDR_DOCUMENTXMLTREEVIEWER_JS" file="../renderer/core/xml/DocumentXMLTreeViewer.js" type="BINDATA" compress="gzip"/>
       <include name="IDR_VALIDATION_BUBBLE_ICON" file="../renderer/core/html/forms/resources/input_alert.svg" type="BINDATA" compress="gzip"/>
-      <include name="IDR_VALIDATION_BUBBLE_CSS" file="${cwd}/${blink_core_output_dir}/validation_bubble.css" type="BINDATA" compress="gzip"/>
+      <include name="IDR_VALIDATION_BUBBLE_CSS" file="../renderer/core/html/forms/resources/validation_bubble.css" type="BINDATA" compress="gzip"/>
       <if expr="not is_android">
         <include name="IDR_PICKER_COMMON_JS" file="../renderer/core/html/forms/resources/pickerCommon.js" type="BINDATA" compress="gzip"/>
         <include name="IDR_PICKER_COMMON_CSS" file="../renderer/core/html/forms/resources/pickerCommon.css" type="BINDATA" compress="gzip"/>
@@ -64,10 +62,8 @@
         <include name="IDR_LIST_PICKER_JS" file="../renderer/core/html/forms/resources/listPicker.js" type="BINDATA" compress="gzip"/>
       </if>
       <include name="IDR_AUDIO_SPATIALIZATION_COMPOSITE" file="../renderer/platform/audio/resources/Composite.flac" type="BINDATA"/>
-
       <!-- Layered API scripts. -->
       <part file="../renderer/core/script/resources/layered_api/resources.grdp" />
-
     </includes>
   </release>
 </grit>

third_party/blink/renderer/build/scripts/minimize_css.py

-#!/usr/bin/env python
-# Copyright 2016 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 functools
-import os.path
-import re
-import sys
-
-import in_generator
-
-
-class CSSMinimizer(object):
-
-    INITIAL = 0
-    MAYBE_COMMENT_START = 1
-    INSIDE_COMMENT = 2
-    MAYBE_COMMENT_END = 3
-    INSIDE_SINGLE_QUOTE = 4
-    INSIDE_SINGLE_QUOTE_ESCAPE = 5
-    INSIDE_DOUBLE_QUOTE = 6
-    INSIDE_DOUBLE_QUOTE_ESCAPE = 7
-
-    def __init__(self):
-        self._output = ''
-        self._codeblock = ''
-
-    def flush_codeblock(self):
-        stripped = re.sub(r"\s+", ' ', self._codeblock)
-        stripped = re.sub(r";?\s*(?P<op>[{};])\s*", r'\g<op>', stripped)
-        self._output += stripped
-        self._codeblock = ''
-
-    def parse(self, content):
-        state = self.INITIAL
-        for char in content:
-            if state == self.INITIAL:
-                if char == '/':
-                    state = self.MAYBE_COMMENT_START
-                elif char == "'":
-                    self.flush_codeblock()
-                    self._output += char
-                    state = self.INSIDE_SINGLE_QUOTE
-                elif char == '"':
-                    self.flush_codeblock()
-                    self._output += char
-                    state = self.INSIDE_DOUBLE_QUOTE
-                else:
-                    self._codeblock += char
-            elif state == self.MAYBE_COMMENT_START:
-                if char == '*':
-                    self.flush_codeblock()
-                    state = self.INSIDE_COMMENT
-                else:
-                    self._codeblock += '/' + char
-                    state = self.INITIAL
-            elif state == self.INSIDE_COMMENT:
-                if char == '*':
-                    state = self.MAYBE_COMMENT_END
-                else:
-                    pass
-            elif state == self.MAYBE_COMMENT_END:
-                if char == '/':
-                    state = self.INITIAL
-                else:
-                    state = self.INSIDE_COMMENT
-            elif state == self.INSIDE_SINGLE_QUOTE:
-                if char == '\\':
-                    self._output += char
-                    state = self.INSIDE_SINGLE_QUOTE_ESCAPE
-                elif char == "'":
-                    self._output += char
-                    state = self.INITIAL
-                else:
-                    self._output += char
-            elif state == self.INSIDE_SINGLE_QUOTE_ESCAPE:
-                self._output += char
-                state = self.INSIDE_SINGLE_QUOTE
-            elif state == self.INSIDE_DOUBLE_QUOTE:
-                if char == '\\':
-                    self._output += char
-                    state = self.INSIDE_DOUBLE_QUOTE_ESCAPE
-                elif char == '"':
-                    self._output += char
-                    state = self.INITIAL
-                else:
-                    self._output += char
-            elif state == self.INSIDE_DOUBLE_QUOTE_ESCAPE:
-                self._output += char
-                state = self.INSIDE_DOUBLE_QUOTE
-
-        self.flush_codeblock()
-        self._output = self._output.strip()
-        return self._output
-
-    @classmethod
-    def minimize_css(cls, content):
-        minimizer = CSSMinimizer()
-        return minimizer.parse(content)
-
-
-class CSSMinimizerWriter(in_generator.GenericWriter):
-
-    def __init__(self, in_file_paths):
-        super(CSSMinimizerWriter, self).__init__(in_file_paths)
-
-        self._outputs = {}
-        for in_file_path in in_file_paths:
-            out_path = os.path.basename(in_file_path)
-            self._outputs[out_path] = functools.partial(self.generate_implementation, in_file_path)
-
-    def generate_implementation(self, in_file_path):
-        content = ''
-        with open(os.path.abspath(in_file_path)) as in_file:
-            content = in_file.read()
-        return CSSMinimizer.minimize_css(content)
-
-
-if __name__ == '__main__':
-    in_generator.Maker(CSSMinimizerWriter).main(sys.argv)

third_party/blink/renderer/core/BUILD.gn

@@ -807,61 +807,6 @@ make_qualified_names("make_core_generated_xml_names") {
 
 # One-off scripts --------------------------------------------------------------
 
-action("make_minimized_css") {
-  script = "../build/scripts/minimize_css.py"
-
-  inputs = [
-    "css/fullscreen.css",
-    "css/fullscreenAndroid.css",
-    "css/mathml.css",
-    "css/svg.css",
-    "css/view-source.css",
-    "css/viewportAndroid.css",
-    "css/viewportTelevision.css",
-    "css/xhtmlmp.css",
-    "html/forms/resources/validation_bubble.css",
-    "html/resources/android.css",
-    "html/resources/forced_colors.css",
-    "html/resources/html.css",
-    "html/resources/input_multiple_fields.css",
-    "html/resources/linux.css",
-    "html/resources/quirks.css",
-    "html/resources/win.css",
-    "html/resources/win_quirks.css",
-    "inspector/inspect_tool_common.css",
-    "xml/DocumentXMLTreeViewer.css",
-  ]
-  outputs = [
-    "$blink_core_output_dir/fullscreen.css",
-    "$blink_core_output_dir/fullscreenAndroid.css",
-    "$blink_core_output_dir/mathml.css",
-    "$blink_core_output_dir/svg.css",
-    "$blink_core_output_dir/view-source.css",
-    "$blink_core_output_dir/viewportAndroid.css",
-    "$blink_core_output_dir/viewportTelevision.css",
-    "$blink_core_output_dir/xhtmlmp.css",
-    "$blink_core_output_dir/validation_bubble.css",
-    "$blink_core_output_dir/android.css",
-    "$blink_core_output_dir/forced_colors.css",
-    "$blink_core_output_dir/html.css",
-    "$blink_core_output_dir/input_multiple_fields.css",
-    "$blink_core_output_dir/linux.css",
-    "$blink_core_output_dir/quirks.css",
-    "$blink_core_output_dir/win.css",
-    "$blink_core_output_dir/win_quirks.css",
-    "$blink_core_output_dir/inspect_tool_common.css",
-    "$blink_core_output_dir/DocumentXMLTreeViewer.css",
-  ]
-
-  args = [
-    "--output_dir",
-    rel_blink_core_gen_dir,
-  ]
-  args += rebase_path(inputs, root_build_dir)
-
-  deps = make_core_generated_deps
-}
-
 action("make_core_generated_html_entity_table") {
   visibility = []  # Allow re-assignment of list.
   visibility = [ ":*" ]

tools/grit/grit/format/minifier.py

@@ -10,19 +10,27 @@ import subprocess
 import sys
 
 __js_minifier = None
-
+__css_minifier = None
 
 def SetJsMinifier(minifier):
   global __js_minifier
   __js_minifier = minifier.split()
 
+def SetCssMinifier(minifier):
+  global __css_minifier
+  __css_minifier = minifier.split()
 
 def Minify(source, filename):
   file_type = path.splitext(filename)[1]
-  if not file_type == '.js' or not __js_minifier:
+  minifier = None
+  if file_type == '.js':
+    minifier = __js_minifier
+  elif file_type == '.css':
+    minifier = __css_minifier
+  if not minifier:
     return source
   p = subprocess.Popen(
-      __js_minifier,
+      minifier,
       stdin=subprocess.PIPE,
       stdout=subprocess.PIPE,
       stderr=subprocess.PIPE)

tools/grit/grit/tool/build.py

@@ -136,6 +136,12 @@ Options:
                     minified Javascript to standard output. A non-zero exit
                     status will be taken as indicating failure.
 
+  --css-minifier    A command to run the CSS minifier. If not set then CSS won't
+                    be minified. The command should read the original CSS from
+                    standard input, and output the minified CSS to standard
+                    output. A non-zero exit status will be taken as indicating
+                    failure.
+
   --brotli          The full path to the brotli executable generated by
                     third_party/brotli/BUILD.gn, required if any entries use
                     compress="brotli".
@@ -165,13 +171,14 @@ are exported to translation interchange files (e.g. XMB files), etc.
     write_only_new = False
     depend_on_stamp = False
     js_minifier = None
+    css_minifier = None
     replace_ellipsis = True
     (own_opts, args) = getopt.getopt(
         args, 'a:p:o:D:E:f:w:t:',
         ('depdir=', 'depfile=', 'assert-file-list=', 'help',
          'output-all-resource-defines', 'no-output-all-resource-defines',
          'no-replace-ellipsis', 'depend-on-stamp', 'js-minifier=',
-         'write-only-new=', 'whitelist-support', 'brotli='))
+         'css-minifier=', 'write-only-new=', 'whitelist-support', 'brotli='))
     for (key, val) in own_opts:
       if key == '-a':
         assert_output_files.append(val)
@@ -209,6 +216,8 @@ are exported to translation interchange files (e.g. XMB files), etc.
         depend_on_stamp = True
       elif key == '--js-minifier':
         js_minifier = val
+      elif key == '--css-minifier':
+        css_minifier = val
       elif key == '--whitelist-support':
         whitelist_support = True
       elif key == '--brotli':
@@ -235,6 +244,9 @@ are exported to translation interchange files (e.g. XMB files), etc.
     if js_minifier:
       minifier.SetJsMinifier(js_minifier)
 
+    if css_minifier:
+      minifier.SetCssMinifier(css_minifier)
+
     self.write_only_new = write_only_new
 
     self.res = grd_reader.Parse(opts.input,

tools/grit/grit_rule.gni

@@ -226,6 +226,7 @@ if (current_toolchain != host_toolchain) {
 
 _strip_resource_files = is_android && is_official_build
 _js_minifier = "//tools/grit/minify_with_uglify.py"
+_css_minifier = "//tools/grit/minimize_css.py"
 
 grit_resource_id_file = "//tools/gritsettings/resource_ids"
 grit_info_script = "//tools/grit/grit_info.py"
@@ -407,12 +408,16 @@ template("grit") {
     }
     if (_strip_resource_files) {
       js_minifier_command = rebase_path(_js_minifier, root_build_dir)
+      css_minifier_command = rebase_path(_css_minifier, root_build_dir)
       args += [
         "--js-minifier",
         js_minifier_command,
+        "--css-minifier",
+        css_minifier_command,
       ]
       inputs += [
         _js_minifier,
+        _css_minifier,
         "//third_party/closure_compiler/compiler/compiler.jar",
       ]
     }

tools/grit/minimize_css.py

+#!/usr/bin/env python
+# Copyright 2016 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 re
+import sys
+
+class CSSMinimizer(object):
+
+  INITIAL = 0
+  MAYBE_COMMENT_START = 1
+  INSIDE_COMMENT = 2
+  MAYBE_COMMENT_END = 3
+  INSIDE_SINGLE_QUOTE = 4
+  INSIDE_SINGLE_QUOTE_ESCAPE = 5
+  INSIDE_DOUBLE_QUOTE = 6
+  INSIDE_DOUBLE_QUOTE_ESCAPE = 7
+
+  def __init__(self):
+    self._output = ''
+    self._codeblock = ''
+
+  def flush_codeblock(self):
+    stripped = re.sub(r"\s+", ' ', self._codeblock)
+    stripped = re.sub(r";?\s*(?P<op>[{};])\s*", r'\g<op>', stripped)
+    self._output += stripped
+    self._codeblock = ''
+
+  def parse(self, content):
+    state = self.INITIAL
+    for char in content:
+      if state == self.INITIAL:
+        if char == '/':
+          state = self.MAYBE_COMMENT_START
+        elif char == "'":
+          self.flush_codeblock()
+          self._output += char
+          state = self.INSIDE_SINGLE_QUOTE
+        elif char == '"':
+          self.flush_codeblock()
+          self._output += char
+          state = self.INSIDE_DOUBLE_QUOTE
+        else:
+          self._codeblock += char
+      elif state == self.MAYBE_COMMENT_START:
+        if char == '*':
+          self.flush_codeblock()
+          state = self.INSIDE_COMMENT
+        else:
+          self._codeblock += '/' + char
+          state = self.INITIAL
+      elif state == self.INSIDE_COMMENT:
+        if char == '*':
+          state = self.MAYBE_COMMENT_END
+        else:
+          pass
+      elif state == self.MAYBE_COMMENT_END:
+        if char == '/':
+          state = self.INITIAL
+        else:
+          state = self.INSIDE_COMMENT
+      elif state == self.INSIDE_SINGLE_QUOTE:
+        if char == '\\':
+          self._output += char
+          state = self.INSIDE_SINGLE_QUOTE_ESCAPE
+        elif char == "'":
+          self._output += char
+          state = self.INITIAL
+        else:
+          self._output += char
+      elif state == self.INSIDE_SINGLE_QUOTE_ESCAPE:
+        self._output += char
+        state = self.INSIDE_SINGLE_QUOTE
+      elif state == self.INSIDE_DOUBLE_QUOTE:
+        if char == '\\':
+          self._output += char
+          state = self.INSIDE_DOUBLE_QUOTE_ESCAPE
+        elif char == '"':
+          self._output += char
+          state = self.INITIAL
+        else:
+          self._output += char
+      elif state == self.INSIDE_DOUBLE_QUOTE_ESCAPE:
+        self._output += char
+        state = self.INSIDE_DOUBLE_QUOTE
+
+    self.flush_codeblock()
+    self._output = self._output.strip()
+    return self._output
+
+  @classmethod
+  def minimize_css(cls, content):
+    minimizer = CSSMinimizer()
+    return minimizer.parse(content)
+
+def main():
+  result = ''
+  try:
+    result = CSSMinimizer.minimize_css(sys.stdin.read())
+  finally:
+    print(result)
+
+if __name__ == '__main__':
+  main()