Add HeadlessTabSocket

headless/lib/renderer/headless_content_renderer_client.cc

Index: headless/lib/renderer/headless_content_renderer_client.cc
diff --git a/headless/lib/renderer/headless_content_renderer_client.cc b/headless/lib/renderer/headless_content_renderer_client.cc
index c4c263e62a728378c6b8c298ffc0ae40b55c1dc7..2d3e34548acc779b09503a0dee45cb8fe99ce78f 100644
--- a/headless/lib/renderer/headless_content_renderer_client.cc
+++ b/headless/lib/renderer/headless_content_renderer_client.cc
@@ -5,6 +5,9 @@
 #include "headless/lib/renderer/headless_content_renderer_client.h"
 
 #include "base/memory/ptr_util.h"
+#include "base/strings/utf_string_conversions.h"
+#include "content/public/common/bindings_policy.h"
+#include "content/public/renderer/render_frame.h"
 #include "printing/features/features.h"
 
 #if BUILDFLAG(ENABLE_BASIC_PRINTING)
@@ -26,4 +29,60 @@ void HeadlessContentRendererClient::RenderFrameCreated(
 #endif
 }
 
+void HeadlessContentRendererClient::RunScriptsAtDocumentStart(
+    content::RenderFrame* render_frame) {
+  if (render_frame->GetEnabledBindings() &

[Sami, 2017/04/12 14:18:46]

nit: Could be an early out to reduce the indentation

[alex clarke (OOO till 29th), 2017/04/12 15:47:46]

Done.

+      content::BindingsPolicy::BINDINGS_POLICY_HEADLESS) {
+    render_frame->ExecuteJavaScript(base::UTF8ToUTF16(R"(
+        (function() {
+        let tabSocket_ = null;
+        let messages_to_send_ = [];

[Sami, 2017/04/12 14:18:46]

nit: messagesToSend

[alex clarke (OOO till 29th), 2017/04/12 15:47:46]

Done.

+        let listener_ = null;
+
+        function getNextEmbedderMessage() {
+          tabSocket_.awaitNextMessageFromEmbedder().then(
+              function(result) {
+                listener_(result.message);
+                getNextEmbedderMessage();
+              });
+        };
+
+        window.TabSocket = {};
+        window.TabSocket.SendMessageToEmbedder = function(message) {

[Sami, 2017/04/12 14:18:46]

Maybe this should just also be send() to match WebSocket.

[alex clarke (OOO till 29th), 2017/04/12 15:47:46]

Done.

+          if (tabSocket_) {
+            tabSocket_.sendMessageToEmbedder(message);
+          } else {
+            messages_to_send_.push(message);
+          }
+        };
+
+        window.TabSocket.SetListener = function(listener) {

[Sami, 2017/04/12 14:18:46]

Could we make the caller set "TabSocket.onmessage = function..." to match the
WebSocket API?

[alex clarke (OOO till 29th), 2017/04/12 15:47:46]

Done.

+          listener_ = listener;
+          if (tabSocket_)
+            getNextEmbedderMessage();
+        };
+
+        // Note define() defines a module in the mojo module dependency
+        // system. While we don't expose our module, the callback below only
+        // fires after the requested modules have been loaded.
+        define([
+            'headless/lib/tab_socket.mojom',
+            'content/public/renderer/frame_interfaces',
+            ], function(tabSocketMojom, frameInterfaces) {
+          tabSocket_ = new tabSocketMojom.TabSocketPtr(
+              frameInterfaces.getInterface(tabSocketMojom.TabSocket.name));
+          // Send any messages that may have been created before the dependency
+          // was resolved.
+          for (var i = 0; i < messages_to_send_.length; i++) {
+            tabSocket_.sendMessageToEmbedder(messages_to_send_[i]);
+          }
+          messages_to_send_ = [];
+          if (listener_)
+            getNextEmbedderMessage();
+        });
+
+        })(); )"));
+  }
+}
+
 }  // namespace headless