Add mojo service for CopylessPaste in Blink

third_party/WebKit/Source/modules/document_metadata/CopylessPasteServer.cpp

+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "modules/document_metadata/CopylessPasteServer.h"
+
+#include "core/frame/LocalFrame.h"
+#include "modules/document_metadata/CopylessPasteExtractor.h"
+#include "mojo/public/cpp/bindings/strong_binding.h"
+
+namespace blink {
+
+CopylessPasteServer::CopylessPasteServer(LocalFrame& frame) : m_frame(frame) {}
+
+void CopylessPasteServer::bindMojoRequest(

[haraken, 2017/03/31 04:20:09]

Would you help me understand why you adopted the bindMojoRequest pattern? I'd
like to understand how CopylessPasteServer is going to be used in the browser
side.

[wychen, 2017/03/31 07:51:54]

For all the visited pages, we want to collect some metadata on the Java side.
The Java side would call the Mojo server in Blink at Tab.onPageLoadFinished(),
and forward the gathered metadata to a system service.

I guess the bindMojoRequest pattern is most suitable for Mojo services that
require its life time persisting across navigations, right?

[haraken, 2017/04/04 06:27:57]

Makes sense.

+    LocalFrame* frame,
+    mojom::blink::CopylessPasteRequest request) {
+  DCHECK(frame);
+
+  mojo::MakeStrongBinding(WTF::makeUnique<CopylessPasteServer>(*frame),
+                          std::move(request));
+}
+
+void CopylessPasteServer::GetEntities(const GetEntitiesCallback& callback) {
+  if (!m_frame || !m_frame->document()) {

[haraken, 2017/03/31 04:20:09]

Instead of doing this, I'd prefer making CopylessPasteServer a ContextClient.
Then you can check if the document has been detached or not by checking
getExecutionContext().

[wychen, 2017/03/31 07:51:54]

I'm still trying to figure out whether it makes more sense to put the Mojo
server in Blink or in the Java side.
Do you think the data flow in the following CL makes more sense?
https://codereview.chromium.org/2709893002/

[haraken, 2017/04/04 06:27:57]

I'd prefer this CL.

Here I'm just asking making CopylessPasteServer inherit from ContextClient, so
that it doesn't need to hold m_frame.

[wychen, 2017/04/05 19:25:50]

I gave it a try using ContextClient, but it seems garbage collection and mojo
isn't particularly compatible, since the binding process requires unique_ptr.

+    callback.Run(mojom::blink::WebPage::New());
+    return;
+  }
+  mojom::blink::WebPagePtr webpage = mojom::blink::WebPage::New();
+  // TODO(wychen): connect with CopylessPasteExtractor::extract() like:
+  // CopylessPasteExtractor::extract(*m_frame->document(), webpage);
+  callback.Run(std::move(webpage));
+}
+
+}  // namespace blink