Introduce NativeExceptionsManager.reportException API

Summary:
@public

`reportException` is a new method on `NativeExceptionsManager` that is designed to allow more structured and flexible JS error reporting. `reportFatalException` and `reportSoftException` are now deprecated.

In addition to all the usual exception fields, `reportException` also accepts an `extraData` property which the JS exception handler can populate with arbitrary JSON-serialisable data (here: the raw stack trace, the current JS engine, and the number of frames popped off the call stack by the exception handler). The contents of `extraData` get attached as JSON to the `JavascriptException` instance (or just logged, in the case of `console.error`).

This change is backwards compatible in two senses:
1. We have a JS fallback that uses `reportFatalException` and `reportSoftException` if the new native method is unavailable.
2. We have a Java fallback that implements `reportFatalException` and `reportSoftException` in terms of `reportException`.

Naturally, both fallbacks mentioned above discard `extraData`.

NOTE: The current implementation is Android-only; for the time being, iOS will continue to use the JS fallback.

While we're in `ExceptionsManager.js`, this also changes `dismissRedbox()` to be optional (which it is, since it's Android-only); existing call sites already guard it with a null check so this requires no other changes.

Reviewed By: mmmulani

Differential Revision: D16133080

fbshipit-source-id: d0b209d58da40b736df63155bbea232e94ce635c

ReactAndroid/src/main/java/com/facebook/react/util/ExceptionDataHelper.java

@@ -0,0 +1,36 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * <p>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.react.util;
+
+import android.util.JsonWriter;
+import com.facebook.react.bridge.JsonWriterHelper;
+import com.facebook.react.bridge.ReadableMap;
+import com.facebook.react.bridge.ReadableType;
+import java.io.IOException;
+import java.io.StringWriter;
+import java.io.Writer;
+import javax.annotation.Nullable;
+
+public class ExceptionDataHelper {
+  static final String EXTRA_DATA_FIELD = "extraData";
+
+  public static String getExtraDataAsJson(@Nullable ReadableMap metadata) {
+    if (metadata == null || metadata.getType(EXTRA_DATA_FIELD) == ReadableType.Null) {
+      return null;
+    }
+    try {
+      Writer extraDataWriter = new StringWriter();
+      JsonWriter json = new JsonWriter(extraDataWriter);
+      JsonWriterHelper.value(json, metadata.getDynamic(EXTRA_DATA_FIELD));
+      json.close();
+      extraDataWriter.close();
+      return extraDataWriter.toString();
+    } catch (IOException ex) {
+    }
+    return null;
+  }
+}