Replace System.loadLibrary with ReLinker.loadLibrary() in FlutterJNI.loadLibrary() (#55095)

Could fix? flutter/flutter#83596

The communication on https://issuetracker.google.com/issues/346717090#comment2 recommends using [ReLinker](https://github.com/KeepSafe/ReLinker) to avoid a bug in how library loading interacts with the [Play delivery feature](https://developer.android.com/guide/playcore/feature-delivery) (used in turn by Flutter's deferred components).

The ReLinker docs also suggest that if you have `minSdk` less than `23`, then you should be using ReLinker regardless, as `System.loadLibrary` is unreliable for other reasons.

I don't have any strong evidence to suggest that either one of these two root causes is the definitive cause of flutter/flutter#83596, but it probably wouldn't hurt � 

[C++, Objective-C, Java style guides]: https://github.com/flutter/engine/blob/main/CONTRIBUTING.md#style

Author: gmackall

DEPS

@@ -780,7 +780,7 @@ deps = {
      'packages': [
        {
         'package': 'flutter/android/embedding_bundle',
-        'version': 'last_updated:2024-06-18T12:13:41-0700'
+        'version': 'last_updated:2024-09-10T16:32:16-0700'
        }
      ],
      'condition': 'download_android_deps',

shell/platform/android/BUILD.gn

@@ -394,6 +394,7 @@ embedding_dependencies_jars = [
   "//flutter/third_party/android_embedding_dependencies/lib/viewpager-1.0.0.jar",
   "//flutter/third_party/android_embedding_dependencies/lib/window-1.2.0.jar",
   "//flutter/third_party/android_embedding_dependencies/lib/window-java-1.2.0.jar",
+  "//flutter/third_party/android_embedding_dependencies/lib/relinker-1.4.5.jar",
 ]
 
 action("check_imports") {

shell/platform/android/io/flutter/embedding/engine/FlutterJNI.java

@@ -24,6 +24,7 @@
 import androidx.annotation.Nullable;
 import androidx.annotation.UiThread;
 import androidx.annotation.VisibleForTesting;
+import com.getkeepsafe.relinker.ReLinker;
 import io.flutter.Log;
 import io.flutter.embedding.engine.FlutterEngine.EngineLifecycleListener;
 import io.flutter.embedding.engine.dart.PlatformMessageHandler;
@@ -139,12 +140,11 @@ public FlutterJNI provideFlutterJNI() {
    *
    * <p>This method should only be called once across all FlutterJNI instances.
    */
-  public void loadLibrary() {
+  public void loadLibrary(Context context) {
     if (FlutterJNI.loadLibraryCalled) {
       Log.w(TAG, "FlutterJNI.loadLibrary called more than once");
     }
-
-    System.loadLibrary("flutter");
+    ReLinker.loadLibrary(context, "flutter");
     FlutterJNI.loadLibraryCalled = true;
   }
 

shell/platform/android/io/flutter/embedding/engine/loader/FlutterLoader.java

@@ -182,7 +182,7 @@ public InitResult call() {
                 ResourceExtractor resourceExtractor = initResources(appContext);
 
                 try {
-                  flutterJNI.loadLibrary();
+                  flutterJNI.loadLibrary(appContext);
                 } catch (UnsatisfiedLinkError unsatisfiedLinkError) {
                   String couldntFindVersion = "couldn't find \"libflutter.so\"";
                   String notFoundVersion = "dlopen failed: library \"libflutter.so\" not found";

shell/platform/android/test/io/flutter/embedding/engine/loader/FlutterLoaderTest.java

@@ -58,7 +58,7 @@ public void itReportsInitializedAfterInitializing() {
     flutterLoader.ensureInitializationComplete(ctx, null);
     shadowOf(getMainLooper()).idle();
     assertTrue(flutterLoader.initialized());
-    verify(mockFlutterJNI, times(1)).loadLibrary();
+    verify(mockFlutterJNI, times(1)).loadLibrary(ctx);
     verify(mockFlutterJNI, times(1)).updateRefreshRate();
   }
 
@@ -70,7 +70,7 @@ public void unsatisfiedLinkErrorPathDoesNotExist() {
 
     Mockito.doThrow(new UnsatisfiedLinkError("couldn't find \"libflutter.so\""))
         .when(mockFlutterJNI)
-        .loadLibrary();
+        .loadLibrary(ctx);
     try {
       flutterLoader.startInitialization(ctx);
     } catch (UnsupportedOperationException e) {

tools/androidx/README.md

@@ -0,0 +1,3 @@
+Defines the additional Android build time dependencies downloaded by `engine/tools/cipd/android_embedding_bundle`, which then get uploaded to CIPD and pulled by `gclient sync` into `third_party/android_embedding_dependencies/lib/`.
+
+Despite the directory name, `files.json` actually includes one non-androidx dependency: [ReLinker](https://github.com/KeepSafe/ReLinker).

tools/androidx/files.json

@@ -86,5 +86,11 @@
     "out_file_name": "core-1.10.3.aar",
     "maven_dependency": "com.google.android.play:core:1.10.3",
     "provides": []
+  },
+  {
+    "url": "https://repo1.maven.org/maven2/com/getkeepsafe/relinker/relinker/1.4.5/relinker-1.4.5.aar",
+    "out_file_name": "relinker-1.4.5.aar",
+    "maven_dependency": "com.getkeepsafe.relinker:relinker:1.4.5",
+    "provides": ["com.getkeepsafe.relinker.ReLinker"]
   }
 ]