[Mojo] Improve JavaScript API for MojoReadMessage

Originally, I tried to make the JavaScript bindings for the core Mojo APIs a
literal translation of the C APIs, but that makes MojoReadMessage a bit awkward
because C needs to worry much more about buffer allocation than JavaScript. In
building towards using the hello_world_service, I found that it was much easier
to push the MojoReadMessage pattern from connector.cc into C++ and make the
JavaScript API a bit more idiomatic by just returning an ArrayBuffer for the
message and an Array of handles.

BUG=317398

Review URL: https://codereview.chromium.org/83143002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@236999 0039d316-1c4b-4281-b951-d872f2087c98

3 files changed, 32 insertions, 16 deletions

diff --git a/gin/converter.cc b/gin/converter.cc
index 5fda673..e60e3a0 100644
--- a/gin/converter.cc
+++ b/gin/converter.cc
@@ -6,6 +6,7 @@
 
 #include "v8/include/v8.h"
 
+using v8::ArrayBuffer;
 using v8::Boolean;
 using v8::External;
 using v8::Function;
@@ -125,6 +126,19 @@ bool Converter<Handle<Object> >::FromV8(Handle<Value> val,
   return true;
 }
 
+Handle<Value> Converter<Handle<ArrayBuffer> >::ToV8(v8::Isolate* isolate,
+                                                    Handle<ArrayBuffer> val) {
+  return val.As<Value>();
+}
+
+bool Converter<Handle<ArrayBuffer> >::FromV8(Handle<Value> val,
+                                             Handle<ArrayBuffer>* out) {
+  if (!val->IsArrayBuffer())
+    return false;
+  *out = Handle<ArrayBuffer>::Cast(val);
+  return true;
+}
+
 Handle<Value> Converter<Handle<External> >::ToV8(v8::Isolate* isolate,
                                                  Handle<External> val) {
   return val.As<Value>();
diff --git a/gin/converter.h b/gin/converter.h
index 33af452..2279319 100644
--- a/gin/converter.h
+++ b/gin/converter.h
@@ -88,6 +88,14 @@ struct Converter<v8::Handle<v8::Object> > {
 };
 
 template<>
+struct Converter<v8::Handle<v8::ArrayBuffer> > {
+  static v8::Handle<v8::Value> ToV8(v8::Isolate* isolate,
+                                    v8::Handle<v8::ArrayBuffer> val);
+  static bool FromV8(v8::Handle<v8::Value> val,
+                     v8::Handle<v8::ArrayBuffer>* out);
+};
+
+template<>
 struct Converter<v8::Handle<v8::External> > {
   static v8::Handle<v8::Value> ToV8(v8::Isolate* isolate,
                                     v8::Handle<v8::External> val);
diff --git a/gin/modules/module_registry.cc b/gin/modules/module_registry.cc
index 8baa482..afb07d3 100644
--- a/gin/modules/module_registry.cc
+++ b/gin/modules/module_registry.cc
@@ -12,6 +12,7 @@
 #include "gin/converter.h"
 #include "gin/per_isolate_data.h"
 #include "gin/public/wrapper_info.h"
+#include "gin/try_catch.h"
 
 using v8::Context;
 using v8::External;
@@ -91,19 +92,6 @@ Handle<String> GetHiddenValueKey(Isolate* isolate) {
   return StringToSymbol(isolate, "::gin::ModuleRegistry");
 }
 
-std::string GetImplicitModuleName(const std::string& explicit_name) {
-  if (!explicit_name.empty())
-    return explicit_name;
-  std::string implicit_name;
-  Handle<StackTrace> trace = StackTrace::CurrentStackTrace(1);
-  if (!trace->GetFrameCount())
-    return implicit_name;
-  Handle<String> script_name = trace->GetFrame(0)->GetScriptName();
-  if (!script_name.IsEmpty())
-    ConvertFromV8(script_name, &implicit_name);
-  return implicit_name;
-}
-
 }  // namespace
 
 ModuleRegistry::ModuleRegistry(Isolate* isolate)
@@ -196,11 +184,17 @@ void ModuleRegistry::Load(Isolate* isolate, scoped_ptr<PendingModule> pending) {
   Handle<Function> factory;
   if (ConvertFromV8(module, &factory)) {
     Handle<Object> global = isolate->GetCurrentContext()->Global();
-    module = factory->Call(global, argc, argv.data());
-    // TODO(abarth): What should we do with exceptions?
+    {
+      gin::TryCatch try_catch;
+      module = factory->Call(global, argc, argv.data());
+      if (try_catch.HasCaught())
+        return;  // TODO(abarth): What should we do with the exception?
+    }
+    if (pending->id.empty())
+      ConvertFromV8(factory->GetScriptOrigin().ResourceName(), &pending->id);
   }
 
-  RegisterModule(isolate, GetImplicitModuleName(pending->id), module);
+  RegisterModule(isolate, pending->id, module);
 }
 
 bool ModuleRegistry::AttemptToLoad(Isolate* isolate,