Limit heap growth on Android

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

@@ -98,7 +98,7 @@ public class FlutterJNI {
 
   // BEGIN Methods related to loading for FlutterLoader.
   /**
-   * Loads the libflutter.so library.
+   * Loads the libflutter.so C++ library.
    *
    * <p>This must be called before any other native methods, and can be overridden by tests to avoid
    * loading native libraries.

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

@@ -60,22 +60,26 @@ public static FlutterLoader getInstance() {
     return instance;
   }
 
+  /** Creates a {@code FlutterLoader} that uses a default constructed {@link FlutterJNI}. */
   public FlutterLoader() {
-    this(null);
+    this(new FlutterJNI());
   }
 
-  public FlutterLoader(@Nullable FlutterJNI flutterJNILoader) {
-    if (flutterJNILoader == null) {
-      flutterJNILoader = new FlutterJNI();
-    }
-    this.flutterJNILoader = flutterJNILoader;
+  /**
+   * Creates a {@code FlutterLoader} with the specified {@link FlutterJNI}.
+   *
+   * @param flutterJNI The {@link FlutterJNI} instance to use for loading the libflutter.so C++
+   *     library, setting up the font manager, and calling into C++ initalization.
+   */
+  public FlutterLoader(@NonNull FlutterJNI flutterJNI) {
+    this.flutterJNI = flutterJNI;
   }
 
   private boolean initialized = false;
   @Nullable private Settings settings;
   private long initStartTimestampMillis;
   private FlutterApplicationInfo flutterApplicationInfo;
-  private FlutterJNI flutterJNILoader;
+  private FlutterJNI flutterJNI;
 
   private static class InitResult {
     final String appStoragePath;
@@ -137,7 +141,7 @@ public void startInitialization(@NonNull Context applicationContext, @NonNull Se
           public InitResult call() {
             ResourceExtractor resourceExtractor = initResources(appContext);
 
-            flutterJNILoader.loadLibrary();
+            flutterJNI.loadLibrary();
 
             // Prefetch the default font manager as soon as possible on a background thread.
             // It helps to reduce time cost of engine setup that blocks the platform thread.
@@ -146,7 +150,7 @@ public InitResult call() {
                     new Runnable() {
                       @Override
                       public void run() {
-                        flutterJNILoader.prefetchDefaultFontManager();
+                        flutterJNI.prefetchDefaultFontManager();
                       }
                     });
 
@@ -242,7 +246,7 @@ public void ensureInitializationComplete(
 
       long initTimeMillis = SystemClock.uptimeMillis() - initStartTimestampMillis;
 
-      flutterJNILoader.init(
+      flutterJNI.init(
           applicationContext,
           shellArgs.toArray(new String[0]),
           kernelPath,

shell/platform/android/test/io/flutter/embedding/engine/PluginComponentTest.java

@@ -32,15 +32,13 @@ public void setUp() {
   @Test
   public void pluginsCanAccessFlutterAssetPaths() {
     // Setup test.
-    FlutterJNI mockFlutterJNILoader = mock(FlutterJNI.class);
+    FlutterJNI mockFlutterJNI = mock(FlutterJNI.class);
     FlutterInjector.setInstance(
-        new FlutterInjector.Builder()
-            .setFlutterLoader(new FlutterLoader(mockFlutterJNILoader))
-            .build());
+        new FlutterInjector.Builder().setFlutterLoader(new FlutterLoader(mockFlutterJNI)).build());
     FlutterJNI flutterJNI = mock(FlutterJNI.class);
     when(flutterJNI.isAttached()).thenReturn(true);
 
-    FlutterLoader flutterLoader = new FlutterLoader(mockFlutterJNILoader);
+    FlutterLoader flutterLoader = new FlutterLoader(mockFlutterJNI);
 
     // Execute behavior under test.
     FlutterEngine flutterEngine =

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

@@ -18,7 +18,8 @@
 import android.app.ActivityManager;
 import android.content.Context;
 import io.flutter.embedding.engine.FlutterJNI;
-import java.util.*;
+import java.util.Arrays;
+import java.util.List;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.mockito.ArgumentCaptor;
@@ -38,21 +39,32 @@ public void itReportsUninitializedAfterCreating() {
 
   @Test
   public void itReportsInitializedAfterInitializing() {
-    FlutterJNI mockFlutterJNILoader = mock(FlutterJNI.class);
-    FlutterLoader flutterLoader = new FlutterLoader(mockFlutterJNILoader);
+    FlutterJNI mockFlutterJNI = mock(FlutterJNI.class);
+    FlutterLoader flutterLoader = new FlutterLoader(mockFlutterJNI);
 
     assertFalse(flutterLoader.initialized());
     flutterLoader.startInitialization(RuntimeEnvironment.application);
     flutterLoader.ensureInitializationComplete(RuntimeEnvironment.application, null);
     shadowOf(getMainLooper()).idle();
     assertTrue(flutterLoader.initialized());
-    verify(mockFlutterJNILoader, times(1)).loadLibrary();
+    verify(mockFlutterJNI, times(1)).loadLibrary();
+  }
+
+  @Test
+  public void itSetsTheOldGenHeapSizeAppropriately() {
+    FlutterJNI mockFlutterJNI = mock(FlutterJNI.class);
+    FlutterLoader flutterLoader = new FlutterLoader(mockFlutterJNI);
+
+    assertFalse(flutterLoader.initialized());
+    flutterLoader.startInitialization(RuntimeEnvironment.application);
+    flutterLoader.ensureInitializationComplete(RuntimeEnvironment.application, null);
+    shadowOf(getMainLooper()).idle();
 
     ActivityManager activityManager =
         (ActivityManager) RuntimeEnvironment.application.getSystemService(Context.ACTIVITY_SERVICE);
     final String oldGenHeapArg = "--old-gen-heap-size=" + activityManager.getLargeMemoryClass();
     ArgumentCaptor<String[]> shellArgsCaptor = ArgumentCaptor.forClass(String[].class);
-    verify(mockFlutterJNILoader, times(1))
+    verify(mockFlutterJNI, times(1))
         .init(
             eq(RuntimeEnvironment.application),
             shellArgsCaptor.capture(),