Win Video Capture: add DirectShow WDM devices capabilities enumeration.

media/video/capture/video_capture_device.h

Index: media/video/capture/video_capture_device.h
diff --git a/media/video/capture/video_capture_device.h b/media/video/capture/video_capture_device.h
index 382dad6cdc461d7d6d20bf04ab8e7e91693ae503..4ce1d3b839b1f707e6c537728984998272b64932 100644
--- a/media/video/capture/video_capture_device.h
+++ b/media/video/capture/video_capture_device.h
@@ -106,6 +106,14 @@ class MEDIA_EXPORT VideoCaptureDevice {
       return capture_api_class_.capture_api_type();
     }
 #endif
+#if defined(OS_WIN)
+    const std::string& capabilities_unique_id() const {

[perkj_chrome, 2014/09/02 09:22:03]

add comment what this id really is and why this is not the same as id().
Should this maybe be names capabilities_id()?

[mcasas, 2014/09/02 15:13:41]

Done.

+      return capabilities_unique_id_;
+    }
+    void set_capabilities_unique_id(const std::string& id) {
+      capabilities_unique_id_ = id;
+    }
+#endif
 #if defined(OS_MACOSX)
     TransportType transport_type() const {
       return transport_type_;
@@ -139,6 +147,10 @@ class MEDIA_EXPORT VideoCaptureDevice {
 
     CaptureApiClass capture_api_class_;
 #endif
+#if defined(OS_WIN)
+    // ID used for capabilities retrieval. By default is equal to |unique_id|.
+    std::string capabilities_unique_id_;
+#endif
 #if defined(OS_MACOSX)
     TransportType transport_type_;
     // Flag used to mark blacklisted devices for QTKit Api.