Fix potential incorrect sync flags used with screenshare TL stream.

webrtc/modules/video_coding/codecs/vp8/default_temporal_layers.cc

Index: webrtc/modules/video_coding/codecs/vp8/default_temporal_layers.cc
diff --git a/webrtc/modules/video_coding/codecs/vp8/default_temporal_layers.cc b/webrtc/modules/video_coding/codecs/vp8/default_temporal_layers.cc
index b161560d42a2427ca494a39d3ce78f3ea8524f4e..010df5b15f02155b85a95ebca36efb1d1f39ad03 100644
--- a/webrtc/modules/video_coding/codecs/vp8/default_temporal_layers.cc
+++ b/webrtc/modules/video_coding/codecs/vp8/default_temporal_layers.cc
@@ -25,7 +25,8 @@
 
 namespace webrtc {
 
-TemporalLayers::FrameConfig::FrameConfig() {}
+TemporalLayers::FrameConfig::FrameConfig()
+    : FrameConfig(kNone, kNone, kNone, false) {}
 
 TemporalLayers::FrameConfig::FrameConfig(TemporalLayers::BufferFlags last,
                                          TemporalLayers::BufferFlags golden,
@@ -48,7 +49,9 @@ TemporalLayers::FrameConfig::FrameConfig(TemporalLayers::BufferFlags last,
       last_buffer_flags(last),
       golden_buffer_flags(golden),
       arf_buffer_flags(arf),
-      freeze_entropy(freeze_entropy) {}
+      layer_sync(false),
+      freeze_entropy(freeze_entropy),
+      pattern_idx(0) {}
 
 namespace {