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

lib/common/buffer-utils.js

@@ -26,25 +26,31 @@ function getType (value) {
   return null
 }
 
+function getBuffer (value) {
+  if (value instanceof Buffer) {
+    return value
+  } else if (value instanceof ArrayBuffer) {
+    return Buffer.from(value)
+  } else {
+    return Buffer.from(value.buffer, value.byteOffset, value.byteLength)
+  }
+}
+
 exports.isBuffer = function (value) {
   return ArrayBuffer.isView(value) || value instanceof ArrayBuffer
 }
 
 exports.bufferToMeta = function (value) {
-  const buffer = (value instanceof ArrayBuffer)
-    ? Buffer.from(value)
-    : Buffer.from(value.buffer, value.byteOffset, value.byteLength)
-
   return {
     type: getType(value),
-    data: buffer.toString('base64'),
+    data: getBuffer(value),
     length: value.length
   }
 }
 
 exports.metaToBuffer = function (value) {
   const constructor = typedArrays[value.type]
-  const data = Buffer.from(value.data, 'base64')
+  const data = getBuffer(value.data)
 
   if (constructor === Buffer) {
     return data