Update android_embedding_bundle CIPD instructions (flutter#44644)

This PR updates the gradle build file for the android_embedding_bundle
cipd package to fetch license information about the dependencies listed
under `tools/androidx/files.json`. The README file for the
android_embedding_bundle now explains how to fetch the license
information and make sure it's correct in the cipd package.

This PR also pulls a new version of android_embedding_dependencies that
includes a `LICENSE` file.

It turns out that Flutter does not re-ship anything from the embedding
bundle to Flutter end-users. These dependencies are only used to create
a classpath against which we build the Android embedder and in-tree
tests. I've updated docs/comments to clarify that since I was initially
confused about how these were used.

I'm not adding a test that compares the license info fetched from maven
against a checked-in golden, yet. Still thinking about the most
effective way to do that in combination with the steps in the README.

DEPS

@@ -735,7 +735,7 @@ deps = {
      'packages': [
        {
         'package': 'flutter/android/embedding_bundle',
-        'version': 'last_updated:2021-11-23T12:31:07-0800'
+        'version': 'last_updated:2023-08-11T11:35:44-0700'
        }
      ],
      'condition': 'download_android_deps',

ci/licenses_golden/tool_signature

@@ -1,2 +1,2 @@
-Signature: 1e4a09fc0f2117b53a35ad1bb8b9a08d
+Signature: d8b5e1bcc7593e590ac227d01043c4a8
 

tools/androidx/configure.gradle

@@ -5,7 +5,7 @@
 import groovy.json.JsonSlurper
 
 // Configures the embedding dependencies.
-ext.configureDependencies = { engineRootDir, add ->
+ext.configureEmbedderDependencies = { engineRootDir, add ->
     def filesJson = new File(engineRootDir, 'tools/androidx/files.json')
     if (!filesJson.exists()) {
         throw new Exception("${filesJson.absolutePath} not found. Did you provide the wrong engine root directory to configureDependencies?")
@@ -17,3 +17,21 @@ ext.configureDependencies = { engineRootDir, add ->
         add(dependency.maven_dependency)
     }
 }
+
+// Configures the embedding dependencies. To match the logic in
+// generate_pom_file.py, this does not include transitive dependencies since
+// they aren't used by the embedding.
+ext.configureDependencies = { engineRootDir, add ->
+    def filesJson = new File(engineRootDir, 'tools/androidx/files.json')
+    if (!filesJson.exists()) {
+        throw new Exception("${filesJson.absolutePath} not found. Did you provide the wrong engine root directory to configureDependencies?")
+    }
+    def dependencies = new JsonSlurper().parseText(filesJson.text)
+    assert dependencies instanceof List
+    dependencies.each { dependency ->
+        assert dependency.maven_dependency instanceof String
+        if (dependency.provides) {
+            add(dependency.maven_dependency)
+        }
+    }
+}

tools/androidx/files.json

@@ -79,5 +79,11 @@
       "androidx.window.layout.WindowLayoutInfo",
       "androidx.window.layout.WindowInfoRepository"
     ]
+  },
+  {
+    "url": "https://dl.google.com/android/maven2/com/google/android/play/core/1.8.0/core-1.8.0.aar",
+    "out_file_name": "core-1.8.0.aar",
+    "maven_dependency": "com.google.android.play:core:1.8.0",
+    "provides": []
   }
 ]

tools/cipd/android_embedding_bundle/.gitignore

@@ -1,3 +1,4 @@
 # Don't include the jars in the engine repo.
+build/
 lib/
 .gradle

tools/cipd/android_embedding_bundle/README.md

@@ -1,12 +1,34 @@
 # Updating the Embedding Dependencies
 
+The instructions in this README explain how to create a CIPD package that
+contains the build-time dependencies of the Android embedding of the Engine,
+and the dependencies of the in-tree testing framework. The Android embedder is
+shipped to Flutter end-users, but these build-time dependencies are not.
+Therefore, the license script can skip over the destination of the CIPD package
+in an Engine checkout at `src/third_party/android_embedding_dependencies`.
+Even so, the CIPD package should contain a LICENSE file, and the instructions
+below explain how to fetch the license information for the dependencies.
+
 ## Requirements
 
-1. Gradle. If you don't have Gradle installed, you can get it on [https://gradle.org/install/#manually](https://gradle.org/install/#manually).
-2. [Depot tools](http://commondatastorage.googleapis.com/chrome-infra-docs/flat/depot_tools/docs/html/depot_tools_tutorial.html#_setting_up).
+1. If you have a flutter/engine checkout, then you should already have
+[Depot tools](http://commondatastorage.googleapis.com/chrome-infra-docs/flat/depot_tools/docs/html/depot_tools_tutorial.html#_setting_up) on your path.
+1. You should have a copy of `gradle` in a flutter/engine checkout under
+   `src/third_party/gradle/bin/gradle`.
 
 ## Steps
 
-1. Update tools/androidx/files.json. (This file includes the Maven dependencies used to build Flutter apps).
-2. `cd` into this directory.
-3. Run `./generate.sh`.
+1. Update `src/flutter/tools/androidx/files.json`. (This file includes the Maven
+   dependencies used to build Flutter apps).
+1. `cd` into this directory: `src/flutter/tools/cipd/android_embedding_bundle`.
+1. Run `gradle downloadLicenses`
+1. Run `gradle updateDependencies`
+1. Examine the file `./build/reports/license/license-dependency.xml`. If it
+   contains licenses other than "The Apache License, Version 2.0" or something
+   very similar, STOP. Ask Hixie for adivce on how to proceed.
+1. Copy or move the `lib/` directory to `src/third_party/android_embedding_dependencies/`,
+   overwriting its contents, and ensure the Android build still works.
+1. Run `cipd create --pkg-def cipd.yaml -tag last_updated:"$version_tag"` where
+   `$version_tag` is the output of `date +%Y-%m-%dT%T%z`.
+1. Update the `DEPS` file entry for `android_embedding_dependencies` with the
+   new tag: `last_updated:"$version_tag"`.

tools/cipd/android_embedding_bundle/build.gradle

@@ -7,8 +7,6 @@
 //
 // This script downloads the embedding dependencies into a lib/ directory,
 // extract jar files from AARs, so they can be used in gn.
-def destinationDir = "lib"
-
 buildscript {
     repositories {
         google()
@@ -19,6 +17,12 @@ buildscript {
     }
 }
 
+plugins {
+    id "com.github.hierynomus.license-report" version "0.16.1"
+}
+
+def destinationDir = "lib"
+
 allprojects {
     repositories {
         google()
@@ -36,9 +40,14 @@ configurations {
   embedding
 }
 
+println project.buildDir
+
 // Configure the embedding dependencies.
-apply from: new File(rootDir, '../tools/androidx/configure.gradle').absolutePath;
-configureDependencies(new File(rootDir, '../..')) { dependency ->
+// NB: '../../androidx/configure.gradle' is expected to resolve to the path
+// 'src/flutter/tools/androidx', and '../../..' is expected to resolve to the
+// path 'src/flutter'.
+apply from: new File(rootDir, '../../androidx/configure.gradle').absolutePath;
+configureEmbedderDependencies(new File(rootDir, '../../..')) { dependency ->
   dependencies {
      embedding "$dependency"
   }
@@ -76,3 +85,22 @@ task updateDependencies() {
       }
   }
 }
+
+downloadLicenses {
+  ext.apacheTwo = license(
+    'The Apache License, Version 2.0',
+    'http://www.apache.org/licenses/LICENSE-2.0.txt',
+  )
+  aliases = [
+    (apacheTwo) : [
+      'The Apache Software License, Version 2.0',
+      'Apache 2',
+      'Apache License Version 2.0',
+      'Apache License, Version 2.0',
+      'Apache License 2.0',
+      license('Apache License', 'http://www.apache.org/licenses/LICENSE-2.0'),
+      license('Apache License, Version 2.0', 'http://opensource.org/licenses/Apache-2.0'),
+    ],
+  ]
+  dependencyConfiguration = 'embedding'
+}

tools/licenses/lib/paths.dart

@@ -44,7 +44,7 @@ final Set<String> skippedPaths = <String>{
   r'fuchsia/sdk/mac/NOTICE.fuchsia',
   r'fuchsia/sdk/mac/tools',
   r'out', // output of build
-  r'third_party/android_embedding_dependencies', // testing framework for android
+  r'third_party/android_embedding_dependencies', // Not shipped. Used only for the build-time classpath, and for the in-tree testing framework for Android
   r'third_party/android_tools', // excluded on advice
   r'third_party/angle/android',
   r'third_party/angle/doc',