Revert "Perfetto: Reduce max trace buffer size to 300mb to avoid Android browser OOMs"

This reverts commit d66855ad.

Reason for revert: crbug.com/902064, reverting to see if this decreases test failures.

Original change's description:
> Perfetto: Reduce max trace buffer size to 300mb to avoid Android browser OOMs
> 
> Specifically memory.long_running_idle_gmail_background_tbmv2 will OOM
> on Nexus5 devices with this buffer size.
> 
> R=​eseckler@chromium.org
> 
> Bug: 902064
> Change-Id: If8e5529f3000b9a2f3b86abaecb1f219df356575
> Reviewed-on: https://chromium-review.googlesource.com/c/1338889
> Commit-Queue: Eric Seckler <eseckler@chromium.org>
> Reviewed-by: Eric Seckler <eseckler@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#608698}

TBR=oysteine@chromium.org,eseckler@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 902064
Change-Id: I0528cc367fb44cc7814fc3b72b5727a25c04450b
Reviewed-on: https://chromium-review.googlesource.com/c/1357403Reviewed-by: oysteine <oysteine@chromium.org>
Commit-Queue: oysteine <oysteine@chromium.org>
Cr-Commit-Position: refs/heads/master@{#612824}

services/tracing/perfetto/json_trace_exporter.cc

@@ -27,7 +27,6 @@ namespace tracing {
 namespace {
 
 const size_t kTraceEventBufferSizeInBytes = 100 * 1024;
-const size_t kPerfettoRingbufferSizeInKBs = 1024 * 300;
 
 void AppendProtoArrayAsJSON(std::string* out,
                             const perfetto::protos::ChromeTracedValue& array);
@@ -289,7 +288,7 @@ JSONTraceExporter::JSONTraceExporter(const std::string& config,
 
   // Start tracing.
   perfetto::TraceConfig trace_config;
-  trace_config.add_buffers()->set_size_kb(kPerfettoRingbufferSizeInKBs);
+  trace_config.add_buffers()->set_size_kb(4096 * 100);
 
   auto* trace_event_config = trace_config.add_data_sources()->mutable_config();
   trace_event_config->set_name(mojom::kTraceEventDataSourceName);