[Reland] Generate a small JS binary for parsing the X-Client-Data header

This header contains serialized and base64-encoded protocol buffers.
This utility simply base64-decodes the serialized data, and then
parses the proto via compiled JSPB parsing.

THis is a reland of
https://chromium-review.googlesource.com/c/chromium/src/+/2301121, restricting
the new build target to only build on Linux.

R=asvitkine, dpranke@google.com
CC=mathias@chromium.org, yangguo@chromium.org

Bug: 1103854
Change-Id: I30bd4d02f89b250c53c06068ab22e97d7fc279ab
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2316448
Commit-Queue: Ilya Sherman <isherman@chromium.org>
Reviewed-by: Dirk Pranke <dpranke@google.com>
Reviewed-by: Mathias Bynens <mathias@chromium.org>
Auto-Submit: Ilya Sherman <isherman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#791341}

PRESUBMIT.py

@@ -10,6 +10,9 @@ for more details about the presubmit API built into depot_tools.
 
 
 _EXCLUDED_PATHS = (
+    # Generated file.
+    (r"^components[\\/]variations[\\/]proto[\\/]devtools[\\/]"
+     r"client_variations_parser.js"),
     r"^native_client_sdk[\\/]src[\\/]build_tools[\\/]make_rules.py",
     r"^native_client_sdk[\\/]src[\\/]build_tools[\\/]make_simple.py",
     r"^native_client_sdk[\\/]src[\\/]tools[\\/].*.mk",

components/variations/proto/BUILD.gn

@@ -23,4 +23,18 @@ proto_library("proto") {
     "study.proto",
     "variations_seed.proto",
   ]
+
+  # The generated JavaScript bindings are used to build a small, self-contained
+  # parser for ClientVariations in Dev Tools. This parser is used to decode the
+  # X-Client-Data header.
+  generate_javascript = true
+}
+
+# Some of the Windows builders do not support Java, which is a required
+# dependency for this build target. This target is only built manually, so it's
+# fine to limit it to Linux.
+if (is_linux || is_mac) {
+  group("devtools") {
+    deps = [ "devtools" ]
+  }
 }

components/variations/proto/PRESUBMIT.py

+# 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.
+
+"""
+See https://dev.chromium.org/developers/how-tos/depottools/presubmit-scripts
+for more details on the presubmit API built into depot_tools.
+"""
+
+
+def CheckChange(input_api, output_api):
+  """Checks that changes to client_variations.proto are mirrored."""
+  has_proto_update = False
+  has_parser_update = False
+  cwd = input_api.PresubmitLocalPath()
+  for path in input_api.AbsoluteLocalPaths():
+    if not path.startswith(cwd):
+      continue
+    name = input_api.os_path.relpath(path, cwd)
+    if name == 'client_variations.proto':
+      has_proto_update = True
+    elif name == 'devtools/client_variations_parser.js':
+      has_parser_update = True
+
+  results = []
+  if has_proto_update and not has_parser_update:
+    results.append(output_api.PresubmitPromptWarning(
+        'client_variations.proto was changed. Does the JS parser at '
+        'devtools/client_variations_parser.js need to be updated as well?'))
+  return results
+
+
+def CheckChangeOnUpload(input_api, output_api):
+  return CheckChange(input_api, output_api)
+
+
+def CheckChangeOnCommit(input_api, output_api):
+  return []

components/variations/proto/client_variations.proto

@@ -11,6 +11,8 @@ option java_package = "org.chromium.components.variations";
 
 package variations;
 
+// NOTE: If you update this proto, you'll also need to rebuild the JS parser for
+// devtools. See //components/variations/proto/devtools/BUILD.gn for details.
 message ClientVariations {
   // A list of client experiment variation IDs that are active.
   repeated int32 variation_id = 1;

components/variations/proto/devtools/BUILD.gn

+# 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.
+
+import("//third_party/closure_compiler/closure_args.gni")
+import("//third_party/closure_compiler/compile_js.gni")
+
+# Some of the Windows builders do not support Java, which is a required
+# dependency for these build targets. These targets are only built manually, so
+# it's fine to limit them to Linux.
+if (is_linux || is_mac) {
+  # Build this target to generate a small, self-contained utility for parsing a
+  # serialized ClientVariations proto from the X-Client-Data header.
+  #
+  # Run components/variations/proto/devtools/update_client_variations_parser.py
+  # to rebuild the library that is synced into the Dev Tools repository.
+  group("devtools") {
+    deps = [ ":client_variations_parser_uncompiled" ]
+  }
+
+  # Note that the name passed to the `js_binary` rule implicitly defines a
+  # dependency on the file that matches the build rule's name.
+  js_binary("client_variations_parser_uncompiled") {
+    outputs = [ "$target_gen_dir/client_variations_parser_gen.js" ]
+    deps = [ "..:proto_js" ]
+    closure_flags = strict_error_checking_closure_args + [
+                      "compilation_level=ADVANCED_OPTIMIZATIONS",
+                      "browser_featureset_year=2020",
+                      "generate_exports",
+                      "export_local_property_definitions",
+                      "isolation_mode=IIFE",
+                      "jscomp_warning=checkTypes",
+                      "jscomp_warning=deprecatedAnnotations",
+                      "jscomp_warning=deprecated",
+                    ]
+  }
+}

components/variations/proto/devtools/client_variations_parser.js

+/* eslint-disable */
+// 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.
+
+// Note: This is a generated file. Do not edit by hand. Instead, run
+// components/variations/proto/devtools/update_client_variations_parser.py to
+// update.
+
+const gen = {};
+
+// clang-format off
+(function(){var f=this||self;
+function g(a){var b=typeof a;if("object"==b)if(a){if(a instanceof Array)return"array";if(a instanceof Object)return b;var c=Object.prototype.toString.call(a);if("[object Window]"==c)return"object";if("[object Array]"==c||"number"==typeof a.length&&"undefined"!=typeof a.splice&&"undefined"!=typeof a.propertyIsEnumerable&&!a.propertyIsEnumerable("splice"))return"array";if("[object Function]"==c||"undefined"!=typeof a.call&&"undefined"!=typeof a.propertyIsEnumerable&&!a.propertyIsEnumerable("call"))return"function"}else return"null";else if("function"==
+b&&"undefined"==typeof a.call)return"object";return b}function l(a,b){function c(){}c.prototype=b.prototype;a.prototype=new c;a.prototype.constructor=a;a.base=function(e,d,h){for(var m=Array(arguments.length-2),k=2;k<arguments.length;k++)m[k-2]=arguments[k];return b.prototype[d].apply(e,m)}};function n(a){if(Error.captureStackTrace)Error.captureStackTrace(this,n);else{const b=Error().stack;b&&(this.stack=b)}a&&(this.message=String(a))}l(n,Error);n.prototype.name="CustomError";function p(a,b){a=a.split("%s");for(var c="",e=a.length-1,d=0;d<e;d++)c+=a[d]+(d<b.length?b[d]:"%s");n.call(this,c+a[e])}l(p,n);p.prototype.name="AssertionError";function q(a,b){throw new p("Failure"+(a?": "+a:""),Array.prototype.slice.call(arguments,1));};var r=null;function t(a){var b=a.length,c=3*b/4;c%3?c=Math.floor(c):-1!="=.".indexOf(a[b-1])&&(c=-1!="=.".indexOf(a[b-2])?c-2:c-1);var e=new Uint8Array(c),d=0;u(a,function(h){e[d++]=h});return e.subarray(0,d)}
+function u(a,b){function c(L){for(;e<a.length;){var y=a.charAt(e++),z=r[y];if(null!=z)return z;if(!/^[\s\xa0]*$/.test(y))throw Error("Unknown base64 encoding at char: "+y);}return L}v();for(var e=0;;){var d=c(-1),h=c(0),m=c(64),k=c(64);if(64===k&&-1===d)break;b(d<<2|h>>4);64!=m&&(b(h<<4&240|m>>2),64!=k&&b(m<<6&192|k))}}
+function v(){if(!r){r={};for(var a="ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789".split(""),b=["+/=","+/","-_=","-_.","-_"],c=0;5>c;c++)for(var e=a.concat(b[c].split("")),d=0;d<e.length;d++){var h=e[d];void 0===r[h]&&(r[h]=d)}}};function w(a){if(a.constructor===Uint8Array)return a;if(a.constructor===ArrayBuffer)return new Uint8Array(a);if("undefined"!=typeof Buffer&&a.constructor===Buffer)return new Uint8Array(a);if(a.constructor===Array)return new Uint8Array(a);if(a.constructor===String)return t(a);q("Type not convertible to Uint8Array.");return new Uint8Array(0)};function x(a){this.b=null;this.a=this.c=this.g=0;a&&A(this,a)}var B=[];function A(a,b){a.b=w(b);a.g=0;a.c=a.b.length;a.a=a.g}x.prototype.reset=function(){this.a=this.g};
+x.prototype.f=function(){var a=this.b;var b=a[this.a];var c=b&127;if(128>b)return this.a+=1,c;b=a[this.a+1];c|=(b&127)<<7;if(128>b)return this.a+=2,c;b=a[this.a+2];c|=(b&127)<<14;if(128>b)return this.a+=3,c;b=a[this.a+3];c|=(b&127)<<21;if(128>b)return this.a+=4,c;b=a[this.a+4];c|=(b&15)<<28;if(128>b)return this.a+=5,c>>>0;this.a+=5;128<=a[this.a++]&&128<=a[this.a++]&&128<=a[this.a++]&&128<=a[this.a++]&&this.a++;return c};x.prototype.h=x.prototype.f;function C(a){if(B.length){var b=B.pop();a&&A(b,a);a=b}else a=new x(a);this.a=a;this.g=this.a.a;this.b=this.c=-1;this.f=!1}C.prototype.reset=function(){this.a.reset();this.b=this.c=-1};function D(a){var b=a.a;if(b.a==b.c)return!1;(b=a.f)||(b=a.a,b=0>b.a||b.a>b.c);if(b)return q("Decoder hit an error"),!1;a.g=a.a.a;var c=a.a.f();b=c>>>3;c&=7;if(0!=c&&5!=c&&1!=c&&2!=c&&3!=c&&4!=c)return q("Invalid wire type: %s (at position %s)",c,a.g),a.f=!0,!1;a.c=b;a.b=c;return!0}
+function E(a){switch(a.b){case 0:if(0!=a.b)q("Invalid wire type for skipVarintField"),E(a);else{for(a=a.a;a.b[a.a]&128;)a.a++;a.a++}break;case 1:1!=a.b?(q("Invalid wire type for skipFixed64Field"),E(a)):(a=a.a,a.a+=8);break;case 2:if(2!=a.b)q("Invalid wire type for skipDelimitedField"),E(a);else{var b=a.a.f();a=a.a;a.a+=b}break;case 5:5!=a.b?(q("Invalid wire type for skipFixed32Field"),E(a)):(a=a.a,a.a+=4);break;case 3:b=a.c;do{if(!D(a)){q("Unmatched start-group tag: stream EOF");a.f=!0;break}if(4==
+a.b){a.c!=b&&(q("Unmatched end-group tag"),a.f=!0);break}E(a)}while(1);break;default:q("Invalid wire encoding for field.")}};function F(){}var G="function"==typeof Uint8Array,H=Object.freeze?Object.freeze([]):[];function I(a,b){if(b<a.c){b+=a.f;var c=a.a[b];return c===H?a.a[b]=[]:c}if(a.b)return c=a.b[b],c===H?a.b[b]=[]:c}F.prototype.toString=function(){return this.a.toString()};function J(a){var b=a;a=K;b||(b=[]);this.f=-1;this.a=b;a:{if(b=this.a.length){--b;var c=this.a[b];if(!(null===c||"object"!=typeof c||"array"==g(c)||G&&c instanceof Uint8Array)){this.c=b- -1;this.b=c;break a}}this.c=Number.MAX_VALUE}if(a)for(b=0;b<a.length;b++)if(c=a[b],c<this.c)c+=-1,this.a[c]=this.a[c]||H;else{var e=this.c+-1;this.a[e]||(this.b=this.a[e]={});this.b[c]=this.b[c]||H}}l(J,F);var K=[1,3];function M(a){var b="";try{b=atob(a)}catch(e){}a=[];for(var c=0;c<b.length;c++)a.push(b.charCodeAt(c));b=new C(a);for(a=new J;D(b)&&4!=b.b;)switch(b.c){case 1:c=b.a.h();I(a,1).push(c);break;case 3:c=b.a.h();I(a,3).push(c);break;default:E(b)}return{variationIds:I(a,1),triggerVariationIds:I(a,3)}}var N=["parseClientVariations"],O=f;N[0]in O||"undefined"==typeof O.execScript||O.execScript("var "+N[0]);
+for(var P;N.length&&(P=N.shift());)N.length||void 0===M?O[P]&&O[P]!==Object.prototype[P]?O=O[P]:O=O[P]={}:O[P]=M;}).call(gen);
+// clang-format on
+
+export function parseClientVariations(data) {
+  return gen.parseClientVariations(data);
+}

components/variations/proto/devtools/client_variations_parser_uncompiled.js

+// 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.
+
+const ClientVariations = goog.require('proto.variations.ClientVariations');
+
+/**
+ * Parses a serialized ClientVariations proto into a human-readable format.
+ * @param {string} data The serialized ClientVariations proto contents, e.g.
+ *     taken from the X-Client-Data header.
+ * @return {{
+ *   variationIds: !Array<number>,
+ *   triggerVariationIds: !Array<number>,
+ * }}
+ */
+export function parse(data) {
+  let decoded = '';
+  try {
+    decoded = atob(data);
+  } catch (e) {
+    // Nothing to do here -- it's fine to leave `decoded` empty if base64
+    // decoding fails.
+  }
+
+  const bytes = [];
+  for (let i = 0; i < decoded.length; i++) {
+    bytes.push(decoded.charCodeAt(i));
+  }
+
+
+  const parsed = ClientVariations.deserializeBinary(bytes);
+  return {
+    'variationIds': parsed.getVariationIdList(),
+    'triggerVariationIds': parsed.getTriggerVariationIdList(),
+  };
+}
+
+goog.exportSymbol('parseClientVariations', parse);

components/variations/proto/devtools/update_client_variations_parser.py

+# 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.
+
+"""Updates the generated ClientVariations proto parser.
+
+If this script happens not to run correctly in your environment, it should be
+easy to perform the steps manually. This script simply builds a generated file,
+and then copies it into the Chromium checkout, making some simple modifications.
+"""
+
+import argparse
+import os
+
+OUTPUT_TEMPLATE = """\
+/* eslint-disable */
+// 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.
+
+// Note: This is a generated file. Do not edit by hand. Instead, run
+// components/variations/proto/devtools/update_client_variations_parser.py to
+// update.
+
+const gen = {};
+
+// clang-format off
+%s
+// clang-format on
+
+export function parseClientVariations(data) {
+  return gen.parseClientVariations(data);
+}
+"""
+
+
+def main():
+  parser = argparse.ArgumentParser()
+  parser.add_argument(
+      '-t', '--target', default='Default',
+      help='the target build subdirectory under src/out/')
+  args = parser.parse_args()
+
+  cwd = os.path.dirname(__file__)
+  root = os.path.join(cwd, '..', '..', '..', '..')
+  build_dir = os.path.abspath(os.path.join(root, 'out', args.target))
+  cmd = 'autoninja -C %s components/variations/proto/devtools' % build_dir
+  os.system(cmd)
+
+  script_file = os.path.join(
+      build_dir, 'gen', 'components', 'variations', 'proto', 'devtools',
+      'client_variations_parser_gen.js')
+  with open(script_file, 'r') as f:
+    script = f.read().strip()
+  script = script.replace('call(this)', 'call(gen)')
+
+  output_file = os.path.abspath(
+      os.path.join(cwd, 'client_variations_parser.js'))
+  with open(output_file, 'w') as f:
+    f.write(OUTPUT_TEMPLATE % script)
+
+
+if __name__ == '__main__':
+  main()