Reorganise sample into debug/release flavours

Summary:
This makes use of the new no-op package and also structures the app
into release and debug flavours that can be built with and without
Flipper part of the APK.

This was a pretty tedious adventure. I may have missed some corner cases
and also restructured a bunch of seemingly unrelated stuff that was
necessary to respect buck module boundaries.

Reviewed By: jknoxville

Differential Revision: D15148004

fbshipit-source-id: bf81f45105f5f16d17daccb3e8050ee00d69fc35

android/sample/src/release/java/com/facebook/flipper/plugins/example/ExampleFlipperPlugin.java

@@ -0,0 +1,18 @@
+/*
+ *  Copyright (c) 2018-present, Facebook, Inc.
+ *
+ *  This source code is licensed under the MIT license found in the LICENSE
+ *  file in the root directory of this source tree.
+ *
+ */
+package com.facebook.flipper.plugins.example;
+
+import android.app.Activity;
+import com.facebook.flipper.core.FlipperPlugin;
+
+// No-Op implementation to satisfy the interface.
+public class ExampleFlipperPlugin implements FlipperPlugin {
+  public void setActivity(Activity a) {
+    // no-op
+  }
+}

android/sample/src/release/java/com/facebook/flipper/sample/ExampleActions.java

@@ -0,0 +1,19 @@
+/*
+ *  Copyright (c) 2018-present, Facebook, Inc.
+ *
+ *  This source code is licensed under the MIT license found in the LICENSE
+ *  file in the root directory of this source tree.
+ *
+ */
+package com.facebook.flipper.sample;
+
+import okhttp3.OkHttpClient;
+
+public final class ExampleActions {
+
+  public static void sendPostRequest(OkHttpClient client) {}
+
+  public static void sendGetRequest(OkHttpClient client) {}
+
+  public static void sendNotification() {}
+}

android/sample/src/release/java/com/facebook/flipper/sample/FlipperInitializer.java

@@ -0,0 +1,35 @@
+/*
+ *  Copyright (c) 2018-present, Facebook, Inc.
+ *
+ *  This source code is licensed under the MIT license found in the LICENSE
+ *  file in the root directory of this source tree.
+ *
+ */
+package com.facebook.flipper.sample;
+
+import android.content.Context;
+import com.facebook.flipper.core.FlipperClient;
+import java.util.concurrent.TimeUnit;
+import okhttp3.OkHttpClient;
+
+public final class FlipperInitializer {
+  public interface IntializationResult {
+    OkHttpClient getOkHttpClient();
+  }
+
+  public static IntializationResult initFlipperPlugins(Context context, FlipperClient client) {
+    final OkHttpClient okHttpClient =
+        new OkHttpClient.Builder()
+            .connectTimeout(60, TimeUnit.SECONDS)
+            .readTimeout(60, TimeUnit.SECONDS)
+            .writeTimeout(10, TimeUnit.MINUTES)
+            .build();
+
+    return new IntializationResult() {
+      @Override
+      public OkHttpClient getOkHttpClient() {
+        return okHttpClient;
+      }
+    };
+  }
+}