Fix a crash in RWHI

When tracing category "disabled-by-default-viz.surface_id_flow" is
enabled, if the value of local_surface_id_allocation is not set on
visual_properties via RenderWidgetHostImpl::GetVisualProperties,
tracing code throws an error resulting in crash.

This CL fixes this issue by returning default value for
LocalSurfaceIdAllocation if it is not set by
RenderWidgetHostImpl::GetVisualProperties.

Bug: 1022882
Change-Id: I45df560ff35d3f0c51f7c716a5f5fadfd50b5c51
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1906940Reviewed-by: Sadrul Chowdhury <sadrul@chromium.org>
Reviewed-by: Daniel Libby <dlibby@microsoft.com>
Commit-Queue: Sarthak Shah <sarsha@microsoft.com>
Cr-Commit-Position: refs/heads/master@{#714627}

content/browser/renderer_host/render_widget_host_impl.cc

@@ -949,11 +949,15 @@ bool RenderWidgetHostImpl::SynchronizeVisualProperties(
   TRACE_EVENT_WITH_FLOW2(
       TRACE_DISABLED_BY_DEFAULT("viz.surface_id_flow"),
       "RenderWidgetHostImpl::SynchronizeVisualProperties send message",
-      visual_properties->local_surface_id_allocation->local_surface_id()
+      visual_properties->local_surface_id_allocation
+          .value_or(viz::LocalSurfaceIdAllocation())
+          .local_surface_id()
           .submission_trace_id(),
       TRACE_EVENT_FLAG_FLOW_OUT, "message",
       "WidgetMsg_SynchronizeVisualProperties", "local_surface_id",
-      visual_properties->local_surface_id_allocation->local_surface_id()
+      visual_properties->local_surface_id_allocation
+          .value_or(viz::LocalSurfaceIdAllocation())
+          .local_surface_id()
           .ToString());
   visual_properties_ack_pending_ =
       DoesVisualPropertiesNeedAck(old_visual_properties_, *visual_properties);