Added registerStream() for using stream id in getUserMedia()

Media source id returned by `added` event should be registered
before using with `getUserMedia()`. Media source id, e.g.
"screen:0", is permanent until removed, while registered stream id
is a temporary one-time random string accessible only from the
frame that requesting it.

Fixed #4459

docs/For Users/Migration/From 0.12 to 0.13.md

@@ -46,6 +46,10 @@
 + Window options `always-on-top` and `visible-on-all-workspaces` is renamed to [`always_on_top`](../../References/Manifest Format.md#always_on_top) and [`visible_on_all_workspaces`](../../References/Manifest Format.md#visible_on_all_workspaces) respectively in `package.json` or as argument of `Window.open()`.
 + Window is not inherited from `EventEmitter` anymore, but the methods `on()`, `once()`, `removeListener()` and `removeAllListeners()` are still supported.
 
+### Screen
+
++ The `id` obtained by `added`, `orderchanged`, `namechanged`, `thumbnailchanged` should be registered and use the stream id returned by [`registerStream(id)`](../../References/Screen.md#screendesktopcapturemonitorregisterstreamid) before passing to `getUserMedia`. See [Synopsis](../../References/Screen.md#synopsis_1) for the usage.
+
 ### Known issues
 
 + The following window options passed to nw.Window.open() is not effective on Linux: `min_width`, `min_height`, `max_width`, `max_height`, `resizable` for now; try to set them in the callback.

docs/References/Screen.md

@@ -119,34 +119,35 @@ This API behaves similar functions as `Screen.chooseDesktopMedia`. But it doesn'
 ### Synopsis
 
 ```javascript
+var dcm = nw.Screen.DesktopCaptureMonitor;
 nw.Screen.Init();
-nw.Screen.DesktopCaptureMonitor.on("added", function (id, name, order, type) {
+dcm.on("added", function (id, name, order, type) {
    //select first stream and shutdown
    var constraints = {
       audio: {
          mandatory: {
              chromeMediaSource: "system",
-             chromeMediaSourceId: id
+             chromeMediaSourceId: dcm.registerStream(id)
           }
       },
       video: {
          mandatory: {
              chromeMediaSource: 'desktop',
-             chromeMediaSourceId: id,
+             chromeMediaSourceId: dcm.registerStream(id)
          }
       }
   };
 
   // TODO: call getUserMedia with contraints
 
-  nw.Screen.DesktopCaptureMonitor.stop();
+  dcm.stop();
 });
 
-nw.Screen.DesktopCaptureMonitor.on("removed", function (id) { });
-nw.Screen.DesktopCaptureMonitor.on("orderchanged", function (id, new_order, old_order) { });
-nw.Screen.DesktopCaptureMonitor.on("namechanged", function (id, name) { });
-nw.Screen.DesktopCaptureMonitor.on("thumbnailchanged", function (id, thumbnail) { });
-nw.Screen.DesktopCaptureMonitor.start(true, true);
+dcm.on("removed", function (id) { });
+dcm.on("orderchanged", function (id, new_order, old_order) { });
+dcm.on("namechanged", function (id, name) { });
+dcm.on("thumbnailchanged", function (id, thumbnail) { });
+dcm.start(true, true);
 ```
 
 ### Screen.DesktopCaptureMonitor.started
@@ -162,42 +163,58 @@ The `DesktopCaptureMonitor` will start monitoring the system and trigger the the
 
 ### Screen.DesktopCaptureMonitor.stop()
 
-The `DesktopCaptureMonitor` will stop monitoring the system. The `id` provided can be passed into `chromeMediaSourceId` in `getUserMedia` constraints. `DesktopCaptureMonitor` should be stopped after a stream is selected.
+The `DesktopCaptureMonitor` will stop monitoring the system. `DesktopCaptureMonitor` should be stopped after a stream is selected.
+
+### Screen.DesktopCaptureMonitor.registerStream(id)
+
+Register and return a valid stream id passed into `chromeMediaSourceId` in `getUserMedia` constraints. See [Synopsis](#synopsis_1) for the usage.
 
 ### Event: added (id, name, order, type, primary)
 
-* `id` `{String}` is unique id that can be passed as chromeMediaSourceId
+!!! warning "Behavior Changed"
+    This feature is changed in 0.13.0. See [Migration Notes from 0.12 to 0.13](../For Users/Migration/From 0.12 to 0.13.md).
+
+* `id` `{String}` is the media id. Use `registerStream(id)` to obtain a valid stream id used with `getUserMedia()`. See [registerStream](#screendesktopcapturemonitorregisterstreamid)
 * `name` `{String}` is the title of the window or screen
 * `order` `{Integer}` is the z-order of the windows, if screens are selected they will appear first
 * `type` `{String}` type of the stream: "screen", "window", "other" or "unknown"
 * `primary` `{Boolean}` _Windows OS only_ this will be `true` if the source is the primary monitor
 
 Emit when a new source was added.
 
-### Event: removed (id)
+### Event: removed (order)
 
-* `id` `{String}` is the chromeMediaSourceId of the screen or monitor that is no longer capturable
+* `order` `{Integer}` is the order of the media source that is no longer capturable
 
 Emit when a source was removed.
 
 ### Event: orderchanged (id, new_order, old_order)
 
-* `id` `{String}` is the chromeMediaSourceId of the screen or window that has changed z-order
+!!! warning "Behavior Changed"
+    This feature is changed in 0.13.0. See [Migration Notes from 0.12 to 0.13](../For Users/Migration/From 0.12 to 0.13.md).
+
+* `id` `{String}` is the media id of the screen or window that has changed z-order
 * `new_order` `{Integer}` is the new z-order
 * `old_order` `{Integer}` is the old z-order
 
 Emit when the Z-order of a source changed (this may change for windows as others are focused).
 
 ### Event: namechanged (id, name)
 
-* `id` `{String}` is the chromeMediaSourceId of the screen or window that has a name changed
+!!! warning "Behavior Changed"
+    This feature is changed in 0.13.0. See [Migration Notes from 0.12 to 0.13](../For Users/Migration/From 0.12 to 0.13.md).
+
+* `id` `{String}` is the media id of the screen or window that has a name changed
 * `name` `{String}` is the new new name of the screen or window
 
 Emit when the name of the source has changed. This can happen when a window changes title.
 
 ### Event: thumbnailchanged (id, thumbnail)
 
-* `id` `{String}` is the chromeMediaSourceId of the screen or window that has an updated thumbnail
+!!! warning "Behavior Changed"
+    This feature is changed in 0.13.0. See [Migration Notes from 0.12 to 0.13](../For Users/Migration/From 0.12 to 0.13.md).
+
+* `id` `{String}` is the media id of the screen or window that has an updated thumbnail
 * `thumbnail` `{String}` is the base64 encoded png of the thumbnail
 
 Emit when the thumbnail of a source changed.

src/api/nw_screen.idl

@@ -46,7 +46,8 @@ namespace nw.Screen {
     [nocompile] static long cancelChooseDesktopMedia(long request_id);
     static void startMonitor(boolean screens, boolean windows);
     static void stopMonitor();
-    static boolean isMonitorStarted();
+    static boolean[] isMonitorStarted();
+    static DOMString[] registerStream(DOMString id);
   };
 
 };

src/api/nw_screen_api.cc

@@ -12,7 +12,12 @@
 #include "base/strings/string16.h"
 #include "base/strings/utf_string_conversions.h"
 #include "chrome/browser/media/desktop_media_list_observer.h"
+#include "chrome/browser/media/desktop_streams_registry.h"
+#include "chrome/browser/media/media_capture_devices_dispatcher.h"
 #include "chrome/browser/media/native_desktop_media_list.h"
+#include "content/public/browser/render_frame_host.h"
+#include "content/public/browser/render_process_host.h"
+#include "content/public/browser/web_contents.h"
 #include "third_party/webrtc/modules/desktop_capture/desktop_capture_options.h"
 #include "third_party/webrtc/modules/desktop_capture/screen_capturer.h"
 #include "third_party/webrtc/modules/desktop_capture/window_capturer.h"
@@ -345,4 +350,36 @@ namespace extensions {
     return true;
   }
 
+  NwScreenRegisterStreamFunction::NwScreenRegisterStreamFunction() {}
+
+  bool NwScreenRegisterStreamFunction::RunNWSync(base::ListValue* response, std::string* error) {
+    std::string id;
+    EXTENSION_FUNCTION_VALIDATE(args_->GetString(0, &id));
+
+    // following code is modified from `DesktopCaptureChooseDesktopMediaFunctionBase::OnPickerDialogResults`
+    // in chrome/browser/extensions/api/desktop_capture/desktop_capture_base.cc
+
+    content::DesktopMediaID source = content::DesktopMediaID::Parse(id);
+    content::WebContents* web_contents = GetSenderWebContents();
+    if (!source.is_null() && web_contents) {
+      std::string result;
+      DesktopStreamsRegistry* registry =
+        MediaCaptureDevicesDispatcher::GetInstance()->
+        GetDesktopStreamsRegistry();
+      // TODO(miu): Once render_frame_host() is being set, we should register the
+      // exact RenderFrame requesting the stream, not the main RenderFrame.  With
+      // that change, also update
+      // MediaCaptureDevicesDispatcher::ProcessDesktopCaptureAccessRequest().
+      // http://crbug.com/304341
+      content::RenderFrameHost* const main_frame = web_contents->GetMainFrame();
+      result = registry->RegisterStream(main_frame->GetProcess()->GetID(),
+                                        main_frame->GetRoutingID(),
+                                        extension()->url(),
+                                        source,
+                                        extension()->name());
+      response->AppendString(result);
+    }
+    return true;
+  }
+
 } // extensions

src/api/nw_screen_api.h

@@ -74,6 +74,20 @@ namespace extensions {
   private:
     DISALLOW_COPY_AND_ASSIGN(NwScreenIsMonitorStartedFunction);
   };
+
+  // implement nw.Screen.registerStream()
+  class NwScreenRegisterStreamFunction : public NWSyncExtensionFunction {
+  public:
+    NwScreenRegisterStreamFunction();
+    bool RunNWSync(base::ListValue* response, std::string* error) override;
+
+  protected:
+    ~NwScreenRegisterStreamFunction() override {}
+    DECLARE_EXTENSION_FUNCTION("nw.Screen.registerStream", UNKNOWN)
+
+  private:
+    DISALLOW_COPY_AND_ASSIGN(NwScreenRegisterStreamFunction);
+  };
 } // extensions
 
 #endif //NW_SRC_API_NW_SCREEN_API_H_

src/resources/api_nw_screen.js

@@ -5,7 +5,7 @@ var EventEmitter = nw.require('events').EventEmitter;
 // Hook Sync API calls
 nw_binding.registerCustomHook(function(bindingsAPI) {
   var apiFunctions = bindingsAPI.apiFunctions;
-  ['getScreens', 'initEventListeners', 'startMonitor', 'stopMonitor', 'isMonitorStarted'].forEach(function(nwSyncAPIName) {
+  ['getScreens', 'initEventListeners', 'startMonitor', 'stopMonitor', 'isMonitorStarted', 'registerStream'].forEach(function(nwSyncAPIName) {
     apiFunctions.setHandleRequest(nwSyncAPIName, function() {
       return sendRequest.sendRequestSync(this.name, arguments, this.definition.parameters, {});
     });
@@ -65,6 +65,9 @@ Screen.cancelChooseDesktopMedia = chrome.desktopCapture.cancelChooseDesktopMedia
 Screen.DesktopCaptureMonitor = new EventEmitter();
 Screen.DesktopCaptureMonitor.start = nwScreenBinding.startMonitor;
 Screen.DesktopCaptureMonitor.stop = nwScreenBinding.stopMonitor;
+Screen.DesktopCaptureMonitor.registerStream = function(id) {
+  return nwScreenBinding.registerStream(id)[0];
+};
 
 Object.defineProperty(Screen.DesktopCaptureMonitor, 'started', {
   get: function() {