Set the max heap size for OSS apps on Android to be 1 GB for Hermes

Summary:
The max heap size currently is 512 MB for OSS apps using Hermes on Android.

Some users (see https://github.com/facebook/hermes/issues/295) are experiencing
long pauses when reaching this ceiling.
Increasing this limit to 1 GB should reduce the frequency of these pauses occurring
for apps where the expected heap usage is near 512 MB.

Changelog: [Internal] Set Hermes's default max heap size to 1 GB

Reviewed By: mhorowitz

Differential Revision: D22577343

fbshipit-source-id: 2d7d688e38e95a082692dca52d010d0449a6e64b

ReactAndroid/src/main/java/com/facebook/hermes/reactexecutor/HermesExecutorFactory.java

@@ -17,7 +17,7 @@ public class HermesExecutorFactory implements JavaScriptExecutorFactory {
   private final RuntimeConfig mConfig;
 
   public HermesExecutorFactory() {
-    this(null);
+    this(new RuntimeConfig(1024));
   }
 
   public HermesExecutorFactory(RuntimeConfig config) {

ReactAndroid/src/main/java/com/facebook/hermes/reactexecutor/RuntimeConfig.java

@@ -11,4 +11,10 @@ package com.facebook.hermes.reactexecutor;
 public final class RuntimeConfig {
   public long heapSizeMB;
   public boolean es6Proxy;
+
+  RuntimeConfig() {}
+
+  RuntimeConfig(long heapSizeMB) {
+    this.heapSizeMB = heapSizeMB;
+  }
 }