[api] Expose Isolate::SetHostImportModuleDynamicallyCallback

This allows embedders to delay initialization of the module system until after
the isolate was created.

BUG=v8:6428
R=gsathya@chromium.org

Review-Url: https://codereview.chromium.org/2897103002
Cr-Commit-Position: refs/heads/master@{#45546}

include/v8.h

@@ -6620,8 +6620,7 @@ class V8_EXPORT Isolate {
           add_histogram_sample_callback(nullptr),
           array_buffer_allocator(nullptr),
           external_references(nullptr),
-          allow_atomics_wait(true),
-          host_import_module_dynamically_callback_(nullptr) {}
+          allow_atomics_wait(true) {}
 
     /**
      * The optional entry_hook allows the host application to provide the
@@ -6684,16 +6683,6 @@ class V8_EXPORT Isolate {
      * this isolate. This can also be configured via SetAllowAtomicsWait.
      */
     bool allow_atomics_wait;
-
-    /**
-     * This is an unfinished experimental feature, and is only exposed
-     * here for internal testing purposes. DO NOT USE.
-     *
-     * This specifies the callback called by the upcoming dynamic
-     * import() language feature to load modules.
-     */
-    HostImportModuleDynamicallyCallback
-        host_import_module_dynamically_callback_;
   };
 
 
@@ -6884,6 +6873,16 @@ class V8_EXPORT Isolate {
   void SetAbortOnUncaughtExceptionCallback(
       AbortOnUncaughtExceptionCallback callback);
 
+  /**
+   * This is an unfinished experimental feature, and is only exposed
+   * here for internal testing purposes. DO NOT USE.
+   *
+   * This specifies the callback called by the upcoming dynamic
+   * import() language feature to load modules.
+   */
+  void SetHostImportModuleDynamicallyCallback(
+      HostImportModuleDynamicallyCallback callback);
+
   /**
    * Optional notification that the system is running low on memory.
    * V8 uses these notifications to guide heuristics.

src/api.cc

@@ -8343,11 +8343,6 @@ Isolate* IsolateNewImpl(internal::Isolate* isolate,
   isolate->set_api_external_references(params.external_references);
   isolate->set_allow_atomics_wait(params.allow_atomics_wait);
 
-  if (params.host_import_module_dynamically_callback_ != nullptr) {
-    isolate->SetHostImportModuleDynamicallyCallback(
-        params.host_import_module_dynamically_callback_);
-  }
-
   SetResourceConstraints(isolate, params.constraints);
   // TODO(jochen): Once we got rid of Isolate::Current(), we can remove this.
   Isolate::Scope isolate_scope(v8_isolate);
@@ -8397,6 +8392,11 @@ void Isolate::SetAbortOnUncaughtExceptionCallback(
   isolate->SetAbortOnUncaughtExceptionCallback(callback);
 }
 
+void Isolate::SetHostImportModuleDynamicallyCallback(
+    HostImportModuleDynamicallyCallback callback) {
+  i::Isolate* isolate = reinterpret_cast<i::Isolate*>(this);
+  isolate->SetHostImportModuleDynamicallyCallback(callback);
+}
 
 Isolate::DisallowJavascriptExecutionScope::DisallowJavascriptExecutionScope(
     Isolate* isolate,

src/d8.cc

@@ -481,9 +481,9 @@ ScriptCompiler::CachedData* CompileForCachedData(
   }
   Isolate::CreateParams create_params;
   create_params.array_buffer_allocator = Shell::array_buffer_allocator;
-  create_params.host_import_module_dynamically_callback_ =
-      Shell::HostImportModuleDynamically;
   Isolate* temp_isolate = Isolate::New(create_params);
+  temp_isolate->SetHostImportModuleDynamicallyCallback(
+      Shell::HostImportModuleDynamically);
   ScriptCompiler::CachedData* result = NULL;
   {
     Isolate::Scope isolate_scope(temp_isolate);
@@ -2313,9 +2313,9 @@ base::Thread::Options SourceGroup::GetThreadOptions() {
 void SourceGroup::ExecuteInThread() {
   Isolate::CreateParams create_params;
   create_params.array_buffer_allocator = Shell::array_buffer_allocator;
-  create_params.host_import_module_dynamically_callback_ =
-      Shell::HostImportModuleDynamically;
   Isolate* isolate = Isolate::New(create_params);
+  isolate->SetHostImportModuleDynamicallyCallback(
+      Shell::HostImportModuleDynamically);
 
   Shell::EnsureEventLoopInitialized(isolate);
   D8Console console(isolate);
@@ -2458,9 +2458,9 @@ void Worker::WaitForThread() {
 void Worker::ExecuteInThread() {
   Isolate::CreateParams create_params;
   create_params.array_buffer_allocator = Shell::array_buffer_allocator;
-  create_params.host_import_module_dynamically_callback_ =
-      Shell::HostImportModuleDynamically;
   Isolate* isolate = Isolate::New(create_params);
+  isolate->SetHostImportModuleDynamicallyCallback(
+      Shell::HostImportModuleDynamically);
   D8Console console(isolate);
   debug::SetConsoleDelegate(isolate, &console);
   {
@@ -3107,9 +3107,6 @@ int Shell::Main(int argc, char* argv[]) {
     create_params.add_histogram_sample_callback = AddHistogramSample;
   }
 
-  create_params.host_import_module_dynamically_callback_ =
-      Shell::HostImportModuleDynamically;
-
   if (i::trap_handler::UseTrapHandler()) {
     if (!v8::V8::RegisterDefaultSignalHandler()) {
       fprintf(stderr, "Could not register signal handler");
@@ -3118,6 +3115,8 @@ int Shell::Main(int argc, char* argv[]) {
   }
 
   Isolate* isolate = Isolate::New(create_params);
+  isolate->SetHostImportModuleDynamicallyCallback(
+      Shell::HostImportModuleDynamically);
 
   D8Console console(isolate);
   {