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/common/native_mate_converters/v8_value_converter.cc

@@ -13,6 +13,7 @@
 #include "base/values.h"
 #include "native_mate/dictionary.h"
 
+#include "atom/common/node_bindings.h"
 #include "atom/common/node_includes.h"
 
 namespace atom {
@@ -136,10 +137,6 @@ void V8ValueConverter::SetStripNullFromObjects(bool val) {
   strip_null_from_objects_ = val;
 }
 
-void V8ValueConverter::SetDisableNode(bool val) {
-  disable_node_ = val;
-}
-
 v8::Local<v8::Value> V8ValueConverter::ToV8Value(
     const base::Value* value,
     v8::Local<v8::Context> context) const {
@@ -253,7 +250,7 @@ v8::Local<v8::Value> V8ValueConverter::ToArrayBuffer(
   const char* data = value->GetBlob().data();
   size_t length = value->GetBlob().size();
 
-  if (!disable_node_) {
+  if (NodeBindings::IsInitialized()) {
     return node::Buffer::Copy(isolate, data, length).ToLocalChecked();
   }