Headless: Support sending and receiving of raw protocol messages

headless/public/headless_devtools_client.h

Index: headless/public/headless_devtools_client.h
diff --git a/headless/public/headless_devtools_client.h b/headless/public/headless_devtools_client.h
index 573336af792ea6e3334851fbd1b648b85bf06476..4bf8380dd1695fb5d40fb4737704e3eaa972e9d1 100644
--- a/headless/public/headless_devtools_client.h
+++ b/headless/public/headless_devtools_client.h
@@ -146,6 +146,25 @@ class HEADLESS_EXPORT HeadlessDevToolsClient {
   virtual target::Domain* GetTarget() = 0;
   virtual tracing::Domain* GetTracing() = 0;
 
+  class HEADLESS_EXPORT RawProtocolListener {
+   public:
+    RawProtocolListener() {}
+    virtual ~RawProtocolListener() {}
+
+    virtual void OnProtocolMessage(

[Sami, 2017/04/12 14:54:24]

This feels a little asymmetric since you send a string but get back both a
string and a dict. How about we make call this as the first thing with just the
raw string and have it return true/false to choose whether the built-in callback
gets called or not?

[alex clarke (OOO till 29th), 2017/04/13 10:46:28]

As discussed offline we added void SendRawDevToolsMessage(const
base::DictionaryValue* message). 

+        const std::string& json_message,
+        const base::DictionaryValue* parsed_message) = 0;
+
+   private:
+    DISALLOW_COPY_AND_ASSIGN(RawProtocolListener);
+  };
+
+  virtual void SetRawProtocolListener(
+      RawProtocolListener* raw_protocol_listener) = 0;
+
+  // The id within the |json_message| must be odd to prevent collisions.
+  virtual void SendRawDevtoolsMessage(const std::string& json_message) = 0;

[Sami, 2017/04/12 14:54:24]

s/Devtools/DevTools/

[alex clarke (OOO till 29th), 2017/04/13 10:46:28]

Done.

+
   // TODO(skyostil): Add notification for disconnection.
 
  private: