Tracing: Removed DCHECK for trace buffer size change in TraceConfig merges

This setting is only used by Perfetto, which doesn't merge configs.

With this DCHECK in place, the trace buffer size can't be configured
through Telemetry as the setting isn't passed through any
command-line switches and hence the DCHECK is hit when the full
config is passed through the full Mojo path and merged with the
startup tracing one. As the option is only used within the tracing
service after startup tracing has already been set up, there's
no point in passing it through the command line and so we just
ignore it instead, if it changes.


R=ssid@chromium.org

Bug: 946517
Change-Id: I56d05dd4f7167dfada4560737d054132d0a47dc4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1548372Reviewed-by: ssid <ssid@chromium.org>
Commit-Queue: oysteine <oysteine@chromium.org>
Cr-Commit-Position: refs/heads/master@{#646617}

base/trace_event/trace_config.cc

@@ -335,8 +335,6 @@ void TraceConfig::Merge(const TraceConfig& config) {
   }
   DCHECK_EQ(trace_buffer_size_in_events_, config.trace_buffer_size_in_events_)
       << "Cannot change trace buffer size";
-  DCHECK_EQ(trace_buffer_size_in_kb_, config.trace_buffer_size_in_kb_)
-      << "Cannot change trace buffer size";
 
   category_filter_.Merge(config.category_filter_);
   memory_dump_config_.Merge(config.memory_dump_config_);