Update Bind to match its comments and always capture by value.

talk/media/webrtc/webrtcvideocapturer.cc

Index: talk/media/webrtc/webrtcvideocapturer.cc
diff --git a/talk/media/webrtc/webrtcvideocapturer.cc b/talk/media/webrtc/webrtcvideocapturer.cc
index 9f1f32af4fe8bfed81726e7e293f2f7a9c60f0d4..c7861baee5ec65f0e6a60e3656847328bb167b25 100644
--- a/talk/media/webrtc/webrtcvideocapturer.cc
+++ b/talk/media/webrtc/webrtcvideocapturer.cc
@@ -383,7 +383,8 @@ void WebRtcVideoCapturer::OnIncomingCapturedFrame(
     // thread hop.
     // Note that Stop() can cause the async invoke call to be cancelled.
     async_invoker_->AsyncInvoke<void>(start_thread_,
-        // Note that this results in a shallow copying of the frame.
+        // Note that Bind captures by value, so there's an intermediate copy
+        // of sample.
         rtc::Bind(&WebRtcVideoCapturer::SignalFrameCapturedOnStartThread,
                   this, sample));
   }
@@ -395,7 +396,7 @@ void WebRtcVideoCapturer::OnCaptureDelayChanged(const int32_t id,
 }
 
 void WebRtcVideoCapturer::SignalFrameCapturedOnStartThread(
-    const webrtc::VideoFrame frame) {
+    const webrtc::VideoFrame& frame) {
   // This can only happen between Start() and Stop().
   RTC_DCHECK(start_thread_);
   RTC_DCHECK(start_thread_->IsCurrent());