fix indexed RAM bundle (#24967)

Summary:
Co-Authored: zamotany
With React Native 0.59.8 the app keeps crashing with indexed RAM bundle on Android with the following error:

```
2019-05-09 11:58:06.684 2793-2856/? E/AndroidRuntime: FATAL EXCEPTION: mqt_js
    Process: com.ramtestapp, PID: 2793
    com.facebook.jni.CppException: getPropertyAsObject: property '__fbRequireBatchedBridge' is not an Object

    no stack
        at com.facebook.react.bridge.queue.NativeRunnable.run(Native Method)
        at android.os.Handler.handleCallback(Handler.java:873)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at com.facebook.react.bridge.queue.MessageQueueThreadHandler.dispatchMessage(MessageQueueThreadHandler.java:29)
        at android.os.Looper.loop(Looper.java:193)
        at com.facebook.react.bridge.queue.MessageQueueThreadImpl$4.run(MessageQueueThreadImpl.java:232)
        at java.lang.Thread.run(Thread.java:764)
```

After investigation we found that when using any bundle, let it be non-ram, FIle RAM bundle or Index RAM bundle, the `CatalystInstanceImpl.java` is always using `loadScriptsFromAsset`, which is calling `CatalystInstanceImpl::jniLoadScriptFromAssets` in C++. This method when checking if bundle is a RAM bundle, uses `JniJSModulesUnbundle::isUnbundle` which only check for js-modules/UNBUNDLE - file generated when building File RAM bundle. There is no other logic to handle Indexed RAM bundle, so it figures that the bundle is not RAM, cause there is no js-modules/UNBUNDLE file and tries to load as regular bundle and fails.

In this PR we added check if it is indexed RAM bundle in `jniLoadScriptFromAssets` and handle it if it is.
## Changelog
[Android] [Fixed] fix indexed RAM bundle

Solves https://github.com/facebook/react-native/issues/21282
Pull Request resolved: https://github.com/facebook/react-native/pull/24967

Differential Revision: D15575924

Pulled By: cpojer

fbshipit-source-id: 5ea428e0b793edd8242243f39f933d1092b35260

ReactCommon/cxxreact/JSIndexedRAMBundle.cpp

@@ -6,7 +6,8 @@
 #include "JSIndexedRAMBundle.h"
 
 #include <glog/logging.h>
-
+#include <fstream>
+#include <sstream>
 #include <folly/Memory.h>
 
 namespace facebook {
@@ -18,14 +19,30 @@ std::function<std::unique_ptr<JSModulesUnbundle>(std::string)> JSIndexedRAMBundl
   };
 }
 
-JSIndexedRAMBundle::JSIndexedRAMBundle(const char *sourcePath) :
-    m_bundle (sourcePath, std::ios_base::in) {
+JSIndexedRAMBundle::JSIndexedRAMBundle(const char *sourcePath) {
+  m_bundle = std::make_unique<std::ifstream>(sourcePath, std::ifstream::binary);
   if (!m_bundle) {
     throw std::ios_base::failure(
       folly::to<std::string>("Bundle ", sourcePath,
-                             "cannot be opened: ", m_bundle.rdstate()));
+                             "cannot be opened: ", m_bundle->rdstate()));
   }
+  init();
+}
 
+JSIndexedRAMBundle::JSIndexedRAMBundle(std::unique_ptr<const JSBigString> script) {
+  // tmpStream is needed because m_bundle is std::istream type
+  // which has no member 'write'
+  std::unique_ptr<std::stringstream> tmpStream = std::make_unique<std::stringstream>();
+  tmpStream->write(script->c_str(), script->size());
+  m_bundle = std::move(tmpStream);
+  if (!m_bundle) {
+    throw std::ios_base::failure(
+      folly::to<std::string>("Bundle from string cannot be opened: ", m_bundle->rdstate()));
+  }
+  init();
+}
+
+void JSIndexedRAMBundle::init() {
   // read in magic header, number of entries, and length of the startup section
   uint32_t header[3];
   static_assert(
@@ -78,12 +95,12 @@ std::string JSIndexedRAMBundle::getModuleCode(const uint32_t id) const {
 }
 
 void JSIndexedRAMBundle::readBundle(char *buffer, const std::streamsize bytes) const {
-  if (!m_bundle.read(buffer, bytes)) {
-    if (m_bundle.rdstate() & std::ios::eofbit) {
+  if (!m_bundle->read(buffer, bytes)) {
+    if (m_bundle->rdstate() & std::ios::eofbit) {
       throw std::ios_base::failure("Unexpected end of RAM Bundle file");
     }
     throw std::ios_base::failure(
-      folly::to<std::string>("Error reading RAM Bundle: ", m_bundle.rdstate()));
+      folly::to<std::string>("Error reading RAM Bundle: ", m_bundle->rdstate()));
   }
 }
 
@@ -92,9 +109,9 @@ void JSIndexedRAMBundle::readBundle(
     const std::streamsize bytes,
     const std::ifstream::pos_type position) const {
 
-  if (!m_bundle.seekg(position)) {
+  if (!m_bundle->seekg(position)) {
     throw std::ios_base::failure(
-      folly::to<std::string>("Error reading RAM Bundle: ", m_bundle.rdstate()));
+      folly::to<std::string>("Error reading RAM Bundle: ", m_bundle->rdstate()));
   }
   readBundle(buffer, bytes);
 }