Add PermissionDescriptor to the permissions Mojo interface.

third_party/WebKit/Source/modules/permissions/PermissionUtils.cpp

+// Copyright 2016 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/permissions/PermissionUtils.h"
+
+#include "core/dom/Document.h"
+#include "core/dom/ExecutionContext.h"
+#include "core/frame/LocalFrame.h"
+#include "public/platform/InterfaceProvider.h"
+#include "public/platform/Platform.h"
+
+namespace blink {
+
+using mojom::blink::PermissionDescriptor;
+using mojom::blink::PermissionDescriptorPtr;
+using mojom::blink::PermissionName;
+
+bool connectToPermissionService(ExecutionContext* executionContext, mojom::blink::PermissionServiceRequest request)
+{
+    InterfaceProvider* interfaceProvider = nullptr;
+    if (executionContext->isDocument()) {
+        Document* document = toDocument(executionContext);
+        if (document->frame())
+            interfaceProvider = document->frame()->interfaceProvider();
+    } else {
+        interfaceProvider = Platform::current()->interfaceProvider();

[haraken, 2016/09/27 13:35:54]

Is it worth distinguishing the interface providers? i.e., what's a disadvantage
of using Platform's interface provider always?

[Reilly Grant (use Gerrit), 2016/09/28 05:22:51]

Platform::interfaceProvider() returns services registered to the
RenderProcessHost, LocalFrame::interfaceProvider() returns services registered
to the RenderFrameHost. Only the later can provide the service with access to
the content::WebContents which is required for displaying UI. A
RenderProcessHost may represent the renderer for multiple tabs.

+    }
+
+    if (interfaceProvider)
+        interfaceProvider->getInterface(std::move(request));
+    return interfaceProvider;
+}
+
+PermissionDescriptorPtr createPermissionDescriptor(PermissionName name)
+{
+    auto descriptor = PermissionDescriptor::New();
+    descriptor->name = name;
+    return descriptor;
+}
+
+PermissionDescriptorPtr createMidiPermissionDescriptor(bool sysex)
+{
+    auto descriptor = createPermissionDescriptor(mojom::blink::PermissionName::MIDI);
+    auto midiExtension = mojom::blink::MidiPermissionDescriptor::New();
+    midiExtension->sysex = sysex;
+    descriptor->extension = mojom::blink::PermissionDescriptorExtension::New();
+    descriptor->extension->set_midi(std::move(midiExtension));
+    return descriptor;
+}
+
+} // namespace blink