[Region Capture] fix blue border in iframes

This patch changes the FSVCI to no longer output a region_capture_rect
whenever the region under capture is embedded in a separate renderer.
This effectively resolves a bug where the blue border is drawn in the
wrong location in this case.

Bug: 1327560
Change-Id: I99a2154f9f455e86df2aaa7151f84178e5202c1e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3699030
Reviewed-by: Elad Alon <eladalon@chromium.org>
Commit-Queue: Jordan Bayles <jophba@chromium.org>
Reviewed-by: Frank Liberato <liberato@chromium.org>
Reviewed-by: Kyle Charbonneau <kylechar@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1014101}

components/viz/service/frame_sinks/video_capture/frame_sink_video_capturer_impl.cc

@@ -971,7 +971,17 @@ void FrameSinkVideoCapturerImpl::MaybeCaptureFrame(
     return;
   }
 
-  if (absl::holds_alternative<RegionCaptureCropId>(target_->sub_target)) {
+  // If the target is in a different renderer than the root renderer (indicated
+  // by having a different frame sink ID), we currently cannot provide
+  // reasonable metadata about the region capture rect. For more context, see
+  // https://crbug.com/1327560.
+  //
+  // TODO(https://crbug.com/1335175): Provide accurate bounds for elements
+  // embedded in different renderers.
+  const bool is_same_frame_sink_as_requested =
+      resolved_target_->GetFrameSinkId() == target_->frame_sink_id;
+  if (absl::holds_alternative<RegionCaptureCropId>(target_->sub_target) &&
+      is_same_frame_sink_as_requested) {
     const float scale_factor = frame_metadata.device_scale_factor;
     metadata.region_capture_rect =
         scale_factor ? ScaleToEnclosingRect(capture_region, 1.0f / scale_factor)

media/base/video_frame_metadata.h

@@ -57,6 +57,10 @@ struct MEDIA_EXPORT VideoFrameMetadata {
   // If cropping was applied due to Region Capture to produce this frame,
   // then this reflects where the frame's contents originate from in the
   // original uncropped frame.
+  //
+  // NOTE: May also be nullopt if region capture is enabled but the capture rect
+  // is in a different coordinate space. For more info, see
+  // https://crbug.com/1327560.
   absl::optional<gfx::Rect> region_capture_rect;
 
   // Whenever cropTo() is called, Blink increments the crop_version and records