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/node_bindings.cc

@@ -104,6 +104,8 @@ void stop_and_close_uv_loop(uv_loop_t* loop) {
   uv_loop_close(loop);
 }
 
+bool g_is_initialized = false;
+
 }  // namespace
 
 namespace atom {
@@ -178,6 +180,10 @@ void NodeBindings::RegisterBuiltinModules() {
 #undef V
 }
 
+bool NodeBindings::IsInitialized() {
+  return g_is_initialized;
+}
+
 void NodeBindings::Initialize() {
   // Open node's error reporting system for browser process.
   node::g_standalone_mode = browser_env_ == BROWSER;
@@ -203,6 +209,8 @@ void NodeBindings::Initialize() {
   if (browser_env_ == BROWSER || env->HasVar("ELECTRON_DEFAULT_ERROR_MODE"))
     SetErrorMode(GetErrorMode() & ~SEM_NOGPFAULTERRORBOX);
 #endif
+
+  g_is_initialized = true;
 }
 
 node::Environment* NodeBindings::CreateEnvironment(