Make getUserMedia() ask for permission if video constraints cannot be satisfied.

content/renderer/media/user_media_client_impl.cc

Index: content/renderer/media/user_media_client_impl.cc
diff --git a/content/renderer/media/user_media_client_impl.cc b/content/renderer/media/user_media_client_impl.cc
index 1ff102e63cf2d33cf5ea60318325dac991b6a813..691e768b3b1c2f186d9b218d774e8466c3bfb73e 100644
--- a/content/renderer/media/user_media_client_impl.cc
+++ b/content/renderer/media/user_media_client_impl.cc
@@ -389,19 +389,26 @@ void UserMediaClientImpl::FinalizeSelectVideoDeviceSourceSettings(
     const RequestSettings& request_settings,
     const VideoCaptureSourceSelectionResult& selection_result) {
   DCHECK(CalledOnValidThread());
-  // Select video device.
-  if (!selection_result.has_value()) {
+  if (selection_result.has_value()) {
+    controls->video.device_id = selection_result.settings.device_id();
+  } else {
+    // TODO(guidou): Abort the request in all cases where |selection_result|
+    // has no value, as the spec mandates.
+    // Currently, some applications rely on the nonstandard behavior of asking
+    // for permission even if constraints cannot be satisfied or there are no
+    // devices. Fix once the standard behavior ceases to be disruptive.
+    // See http://crbug.com/690491.
     blink::WebString failed_constraint_name =
         blink::WebString::fromASCII(selection_result.failed_constraint_name);
-    MediaStreamRequestResult result =
-        failed_constraint_name.isEmpty()
-            ? MEDIA_DEVICE_NO_HARDWARE
-            : MEDIA_DEVICE_CONSTRAINT_NOT_SATISFIED;
-    GetUserMediaRequestFailed(user_media_request, result,
-                              failed_constraint_name);
-    return;
+    blink::WebString device_id_constraint_name = blink::WebString::fromASCII(
+        user_media_request.videoConstraints().basic().deviceId.name());
+    if (failed_constraint_name.equals(device_id_constraint_name)) {
+      GetUserMediaRequestFailed(user_media_request,
+                                MEDIA_DEVICE_CONSTRAINT_NOT_SATISFIED,
+                                failed_constraint_name);
+      return;
+    }
   }
-  controls->video.device_id = selection_result.settings.device_id();
   FinalizeRequestUserMedia(request_id, user_media_request, std::move(controls),
                            request_settings);
 }