perf: don't use JSON to send the result of ipcRenderer.sendSync. (#8953)

* Don't use JSON to send the result of `ipcRenderer.sendSync`.

- Change the return type of AtomViewHostMsg_Message_Sync from `base::string16`
  to `base::ListValue`
- Adjust lib/browser/api/web-contents.js and /lib/renderer/api/ipc-renderer.js
  to wrap/unwrap return values to/from array, instead of
  serializing/deserializing JSON.

This change can greatly improve `ipcRenderer.sendSync` calls where the return
value contains Buffer instances, because those are converted to Array before
being serialized to JSON(which has no efficient way of representing byte
arrays).

A simple benchmark where remote.require('fs') was used to read a 16mb file got
at least 5x faster, not to mention it used a lot less memory.  This difference
tends increases with larger buffers.

* Don't base64 encode Buffers

* Don't allocate V8ValueConverter on the heap

* Replace hidden global.sandbox with NodeBindings::IsInitialized()

* Refactoring: check NodeBindings::IsInitialized() in V8ValueConverter

* Refactor problematic test to make it more reliable

* Add tests for NaN and Infinity

atom/browser/api/event.cc

@@ -6,6 +6,7 @@
 
 #include "atom/common/api/api_messages.h"
 #include "atom/common/native_mate_converters/string16_converter.h"
+#include "atom/common/native_mate_converters/value_converter.h"
 #include "content/public/browser/render_frame_host.h"
 #include "content/public/browser/web_contents.h"
 #include "native_mate/object_template_builder.h"
@@ -52,11 +53,11 @@ void Event::PreventDefault(v8::Isolate* isolate) {
   GetWrapper()->Set(StringToV8(isolate, "defaultPrevented"), v8::True(isolate));
 }
 
-bool Event::SendReply(const base::string16& json) {
+bool Event::SendReply(const base::ListValue& result) {
   if (message_ == nullptr || sender_ == nullptr)
     return false;
 
-  AtomFrameHostMsg_Message_Sync::WriteReplyParams(message_, json);
+  AtomFrameHostMsg_Message_Sync::WriteReplyParams(message_, result);
   bool success = sender_->Send(message_);
   message_ = nullptr;
   sender_ = nullptr;