Make the preemptive compilation threshold configurable

Summary:
This diff allows specifying the preemptive compilation threshold via CompileFlags.
Users get a toggle in CLI and RuntimeConfig that allows choosing between 1. fully eager, 2. fully lazy, 3. use default thresholds ("smart"). The default is #3.

However, since we use `-O` by default, it overrides any lazy compilation when
using the `hermes` binary.

ChangeLog: [Internal] Inspector updated to use new RuntimeConfig laziness control

Reviewed By: tmikov

Differential Revision: D23356463

fbshipit-source-id: 508b7b2e6a218346c69acfec97e7891e388f0e9b

ReactCommon/hermes/inspector/chrome/tests/AsyncHermesRuntime.cpp

@@ -20,12 +20,17 @@ namespace chrome {
 
 namespace detail = facebook::hermes::inspector::detail;
 
-AsyncHermesRuntime::AsyncHermesRuntime()
-    : runtime_(facebook::hermes::makeHermesRuntime()),
-      executor_(
+AsyncHermesRuntime::AsyncHermesRuntime(bool veryLazy)
+    : executor_(
           std::make_unique<detail::SerialExecutor>("async-hermes-runtime")) {
   using namespace std::placeholders;
 
+  auto builder = ::hermes::vm::RuntimeConfig::Builder();
+  if (veryLazy) {
+    builder.withCompilationMode(::hermes::vm::ForceLazyCompilation);
+  }
+  runtime_ = facebook::hermes::makeHermesRuntime(builder.build());
+
   runtime_->global().setProperty(
       *runtime_,
       "shouldStop",

ReactCommon/hermes/inspector/chrome/tests/AsyncHermesRuntime.h

@@ -27,7 +27,9 @@ namespace chrome {
  */
 class AsyncHermesRuntime {
  public:
-  AsyncHermesRuntime();
+  // Create a runtime. If veryLazy, configure the runtime to use completely
+  // lazy compilation.
+  AsyncHermesRuntime(bool veryLazy = false);
   ~AsyncHermesRuntime();
 
   std::shared_ptr<HermesRuntime> runtime() {

ReactCommon/hermes/inspector/chrome/tests/ConnectionTests.cpp

@@ -44,8 +44,8 @@ namespace {
 // the already-deallocated connection.
 class TestContext {
  public:
-  TestContext(bool waitForDebugger = false)
-      : conn_(runtime_.runtime(), waitForDebugger) {}
+  TestContext(bool waitForDebugger = false, bool veryLazy = false)
+      : runtime_(veryLazy), conn_(runtime_.runtime(), waitForDebugger) {}
   ~TestContext() {
     runtime_.wait();
   }
@@ -860,9 +860,6 @@ TEST(ConnectionTests, testSetLazyBreakpoint) {
   SyncConnection &conn = context.conn();
   int msgId = 1;
 
-  facebook::hermes::HermesRuntime::DebugFlags flags{};
-  flags.lazy = true;
-
   asyncRuntime.executeScriptAsync(
       R"(
     var a = 1 + 2;
@@ -879,8 +876,7 @@ TEST(ConnectionTests, testSetLazyBreakpoint) {
 
     foo();
   )",
-      "url",
-      flags);
+      "url");
 
   send<m::debugger::EnableRequest>(conn, msgId++);
   expectExecutionContextCreated(conn);