Trigger R8's ServiceLoader optimization

[ejona86]

Just a sketch, but the neat thing is if we trigger the ServiceLoader optimization, that will keep the constructors for us, so we could use the hard-coded list or the fake-ServiceLoader-iterator and it should work fine either way.

[ejona86]

I proved this works with R8 with optimizations by looking at the dex results. I am keeping it as draft as I need to investigate some potential runtime issues it might cause inside Google due to how the build is structured (related to cl/856425076).

My hacks to get proguard-android-optimize.txt limping along:

diff --git a/android-interop-testing/build.gradle b/android-interop-testing/build.gradle
index 17551465f..cb376e013 100644
--- a/android-interop-testing/build.gradle
+++ b/android-interop-testing/build.gradle
@@ -47,7 +47,7 @@ android {
         debug { minifyEnabled false }
         release {
             minifyEnabled true
-            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
+            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
         }
     }
     lintOptions {
@@ -78,10 +78,10 @@ dependencies {
             libraries.androidx.test.rules,
             libraries.opencensus.contrib.grpc.metrics
 
-    implementation (project(':grpc-services')) {
-        exclude group: 'com.google.protobuf'
-        exclude group: 'com.google.guava'
-    }
+    //implementation (project(':grpc-services')) {
+    //    exclude group: 'com.google.protobuf'
+    //    exclude group: 'com.google.guava'
+    //}
 
     androidTestImplementation 'androidx.test.ext:junit:1.1.3',
             'androidx.test:runner:1.4.0'
diff --git a/interop-testing/src/main/java/io/grpc/testing/integration/TestServiceImpl.java b/interop-testing/src/main/java/io/grpc/testing/integration/TestServiceImpl.java
index a9ee93824..bfd03b08e 100644
--- a/interop-testing/src/main/java/io/grpc/testing/integration/TestServiceImpl.java
+++ b/interop-testing/src/main/java/io/grpc/testing/integration/TestServiceImpl.java
@@ -28,8 +28,8 @@ import io.grpc.ServerInterceptor;
 import io.grpc.Status;
 import io.grpc.StatusRuntimeException;
 import io.grpc.internal.LogExceptionRunnable;
-import io.grpc.services.CallMetricRecorder;
-import io.grpc.services.MetricRecorder;
+//import io.grpc.services.CallMetricRecorder;
+//import io.grpc.services.MetricRecorder;
 import io.grpc.stub.ServerCallStreamObserver;
 import io.grpc.stub.StreamObserver;
 import io.grpc.testing.integration.Messages.Payload;
@@ -65,20 +65,20 @@ public class TestServiceImpl implements io.grpc.BindableService, AsyncService {
 
   private final ScheduledExecutorService executor;
   private final ByteString compressableBuffer;
-  private final MetricRecorder metricRecorder;
+  private final Object metricRecorder;
   final Semaphore lock = new Semaphore(1);
 
   /**
    * Constructs a controller using the given executor for scheduling response stream chunks.
    */
-  public TestServiceImpl(ScheduledExecutorService executor, MetricRecorder metricRecorder) {
+  public TestServiceImpl(ScheduledExecutorService executor, Object metricRecorder) {
     this.executor = executor;
     this.compressableBuffer = ByteString.copyFrom(new byte[1024]);
     this.metricRecorder = metricRecorder;
   }
 
   public TestServiceImpl(ScheduledExecutorService executor) {
-    this(executor, MetricRecorder.newInstance());
+    this(executor, null);//MetricRecorder.newInstance());
   }
 
   @Override
@@ -139,25 +139,25 @@ public class TestServiceImpl implements io.grpc.BindableService, AsyncService {
     responseObserver.onCompleted();
   }
 
-  private static void echoCallMetricsFromPayload(TestOrcaReport report) {
-    CallMetricRecorder recorder = CallMetricRecorder.getCurrent()
-        .recordCpuUtilizationMetric(report.getCpuUtilization())
-        .recordMemoryUtilizationMetric(report.getMemoryUtilization());
-    for (Map.Entry<String, Double> entry : report.getUtilizationMap().entrySet()) {
-      recorder.recordUtilizationMetric(entry.getKey(), entry.getValue());
-    }
-    for (Map.Entry<String, Double> entry : report.getRequestCostMap().entrySet()) {
-      recorder.recordRequestCostMetric(entry.getKey(), entry.getValue());
-    }
+  private static void echoCallMetricsFromPayload(TestOrcaReport unused) {
+    //CallMetricRecorder recorder = CallMetricRecorder.getCurrent()
+    //    .recordCpuUtilizationMetric(report.getCpuUtilization())
+    //    .recordMemoryUtilizationMetric(report.getMemoryUtilization());
+    //for (Map.Entry<String, Double> entry : report.getUtilizationMap().entrySet()) {
+    //  recorder.recordUtilizationMetric(entry.getKey(), entry.getValue());
+    //}
+    //for (Map.Entry<String, Double> entry : report.getRequestCostMap().entrySet()) {
+    //  recorder.recordRequestCostMetric(entry.getKey(), entry.getValue());
+    //}
   }
 
   private void echoMetricsFromPayload(TestOrcaReport report) {
-    metricRecorder.setCpuUtilizationMetric(report.getCpuUtilization());
-    metricRecorder.setMemoryUtilizationMetric(report.getMemoryUtilization());
-    metricRecorder.setAllUtilizationMetrics(new HashMap<>());
-    for (Map.Entry<String, Double> entry : report.getUtilizationMap().entrySet()) {
-      metricRecorder.putUtilizationMetric(entry.getKey(), entry.getValue());
-    }
+    //metricRecorder.setCpuUtilizationMetric(report.getCpuUtilization());
+    //metricRecorder.setMemoryUtilizationMetric(report.getMemoryUtilization());
+    //metricRecorder.setAllUtilizationMetrics(new HashMap<>());
+    //for (Map.Entry<String, Double> entry : report.getUtilizationMap().entrySet()) {
+    //  metricRecorder.putUtilizationMetric(entry.getKey(), entry.getValue());
+    //}
   }
 
   /**