Show bundle loading progress on Android

Summary:
This implements a loading banner like on iOS that shows the progress of the packager.

![](https://media.giphy.com/media/l4FGoepExkpOeXtTO/giphy.gif)

**Test plan**
- Tested that it displays similar messages as it does on iOS and also that is show the right message when waiting for the remote debugger.
- Tested that errors are still shown properly.
- Tested that it works with packagers that don't support multipart response (add && false in https://github.com/facebook/react-native/blob/master/packager/src/Server/MultipartResponse.js#L81).
- Run new unit tests.
- Tested that backgrounding / foregrounding the app hides / show the banner properly.
Closes https://github.com/facebook/react-native/pull/12674

Differential Revision: D4673638

Pulled By: mkonicek

fbshipit-source-id: b2a1163de3d0792cf481d7111231a065f80a9594

ReactAndroid/src/test/java/com/facebook/react/devsupport/BUCK

@@ -16,6 +16,7 @@ rn_robolectric_test(
         react_native_dep("third-party/java/mockito:mockito"),
         react_native_dep("third-party/java/okhttp:okhttp3"),
         react_native_dep("third-party/java/okhttp:okhttp3-ws"),
+        react_native_dep("third-party/java/okio:okio"),
         react_native_dep("third-party/java/robolectric3/robolectric:robolectric"),
         react_native_target("java/com/facebook/react:react"),
         react_native_target("java/com/facebook/react/bridge:bridge"),

ReactAndroid/src/test/java/com/facebook/react/devsupport/MultipartStreamReaderTest.java

@@ -0,0 +1,143 @@
+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+package com.facebook.react.devsupport;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.robolectric.RobolectricTestRunner;
+
+import java.io.IOException;
+import java.util.Map;
+
+import okio.Buffer;
+import okio.ByteString;
+
+import static org.fest.assertions.api.Assertions.assertThat;
+
+@RunWith(RobolectricTestRunner.class)
+public class MultipartStreamReaderTest {
+
+  class CallCountTrackingChunkCallback implements MultipartStreamReader.ChunkCallback {
+    private int mCount = 0;
+
+    @Override
+    public void execute(Map<String, String> headers, Buffer body, boolean done) throws IOException {
+      mCount++;
+    }
+
+    public int getCallCount() {
+      return mCount;
+    }
+  }
+
+  @Test
+  public void testSimpleCase() throws IOException {
+    ByteString response = ByteString.encodeUtf8(
+      "preable, should be ignored\r\n" +
+      "--sample_boundary\r\n" +
+      "Content-Type: application/json; charset=utf-8\r\n" +
+      "Content-Length: 2\r\n\r\n" +
+      "{}\r\n" +
+      "--sample_boundary--\r\n" +
+      "epilogue, should be ignored");
+
+    Buffer source = new Buffer();
+    source.write(response);
+
+    MultipartStreamReader reader = new MultipartStreamReader(source, "sample_boundary");
+
+    CallCountTrackingChunkCallback callback = new CallCountTrackingChunkCallback() {
+      @Override
+      public void execute(Map<String, String> headers, Buffer body, boolean done) throws IOException {
+        super.execute(headers, body, done);
+
+        assertThat(done).isTrue();
+        assertThat(headers.get("Content-Type")).isEqualTo("application/json; charset=utf-8");
+        assertThat(body.readUtf8()).isEqualTo("{}");
+      }
+    };
+    boolean success = reader.readAllParts(callback);
+
+    assertThat(callback.getCallCount()).isEqualTo(1);
+    assertThat(success).isTrue();
+  }
+
+  @Test
+  public void testMultipleParts() throws IOException {
+    ByteString response = ByteString.encodeUtf8(
+      "preable, should be ignored\r\n" +
+      "--sample_boundary\r\n" +
+      "1\r\n" +
+      "--sample_boundary\r\n" +
+      "2\r\n" +
+      "--sample_boundary\r\n" +
+      "3\r\n" +
+      "--sample_boundary--\r\n" +
+      "epilogue, should be ignored");
+
+    Buffer source = new Buffer();
+    source.write(response);
+
+    MultipartStreamReader reader = new MultipartStreamReader(source, "sample_boundary");
+
+    CallCountTrackingChunkCallback callback = new CallCountTrackingChunkCallback() {
+      @Override
+      public void execute(Map<String, String> headers, Buffer body, boolean done) throws IOException {
+        super.execute(headers, body, done);
+
+        assertThat(done).isEqualTo(getCallCount() == 3);
+        assertThat(body.readUtf8()).isEqualTo(String.valueOf(getCallCount()));
+      }
+    };
+    boolean success = reader.readAllParts(callback);
+
+    assertThat(callback.getCallCount()).isEqualTo(3);
+    assertThat(success).isTrue();
+  }
+
+  @Test
+  public void testNoDelimiter() throws IOException {
+    ByteString response = ByteString.encodeUtf8("Yolo");
+
+    Buffer source = new Buffer();
+    source.write(response);
+
+    MultipartStreamReader reader = new MultipartStreamReader(source, "sample_boundary");
+
+    CallCountTrackingChunkCallback callback = new CallCountTrackingChunkCallback();
+    boolean success = reader.readAllParts(callback);
+
+    assertThat(callback.getCallCount()).isEqualTo(0);
+    assertThat(success).isFalse();
+  }
+
+  @Test
+  public void testNoCloseDelimiter() throws IOException {
+    ByteString response = ByteString.encodeUtf8(
+      "preable, should be ignored\r\n" +
+      "--sample_boundary\r\n" +
+      "Content-Type: application/json; charset=utf-8\r\n" +
+      "Content-Length: 2\r\n\r\n" +
+      "{}\r\n" +
+      "--sample_boundary\r\n" +
+      "incomplete message...");
+
+    Buffer source = new Buffer();
+    source.write(response);
+
+    MultipartStreamReader reader = new MultipartStreamReader(source, "sample_boundary");
+
+    CallCountTrackingChunkCallback callback = new CallCountTrackingChunkCallback();
+    boolean success = reader.readAllParts(callback);
+
+    assertThat(callback.getCallCount()).isEqualTo(1);
+    assertThat(success).isFalse();
+  }
+}