[remoting] Simplify DesktopResizerX11::CreateMode().

The new mode ID is returned by the RANDR CreateMode() request, so
there is no need to refresh the resources and search for it.

Bug: 1326339
Change-Id: Ibb0bf991ccfa431c1ead900205d66529a7d08f61
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3839075
Auto-Submit: Lambros Lambrou <lambroslambrou@chromium.org>
Commit-Queue: Jamie Walch <jamiewalch@chromium.org>
Reviewed-by: Jamie Walch <jamiewalch@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1036826}

remoting/host/desktop_resizer_x11.cc

@@ -336,20 +336,14 @@ x11::RandR::Mode DesktopResizerX11::CreateMode(x11::RandR::Output output,
   mode.width = width;
   mode.height = height;
   mode.name_len = name.size();
-  randr_->CreateMode({root_, mode, name.c_str()});
-
-  if (!resources_.Refresh(randr_, root_))
-    return kInvalidMode;
-  x11::RandR::Mode mode_id = resources_.GetIdForMode(name);
-  if (mode_id == kInvalidMode) {
-    LOG(ERROR) << "No ID found for mode: " << name;
-    return kInvalidMode;
+  if (auto reply = randr_->CreateMode({root_, mode, name.c_str()}).Sync()) {
+    randr_->AddOutputMode({
+        output,
+        reply->mode,
+    });
+    return reply->mode;
   }
-  randr_->AddOutputMode({
-      output,
-      mode_id,
-  });
-  return mode_id;
+  return kInvalidMode;
 }
 
 void DesktopResizerX11::DeleteMode(x11::RandR::Output output,