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/renderer/api/atom_api_renderer_ipc.h

@@ -16,9 +16,9 @@ void Send(mate::Arguments* args,
           const base::string16& channel,
           const base::ListValue& arguments);
 
-base::string16 SendSync(mate::Arguments* args,
-                        const base::string16& channel,
-                        const base::ListValue& arguments);
+base::ListValue SendSync(mate::Arguments* args,
+                         const base::string16& channel,
+                         const base::ListValue& arguments);
 
 void Initialize(v8::Local<v8::Object> exports,
                 v8::Local<v8::Value> unused,