Perfetto: Disabled startup tracing usage in background tracing temporarily

Startup tracing is currently causing deadlocks when Perfetto is enabled,
in specific circumstances; since we don't currently need it on Android
when background tracing is used, I'm temporarily disabling it to progress
work on other areas of the pipeline.

R=ssid@chromium.org

Bug: 941318
Change-Id: I97609b059b9469e1a677c490aced9237c5043ff2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1579781
Commit-Queue: ssid <ssid@chromium.org>
Reviewed-by: ssid <ssid@chromium.org>
Cr-Commit-Position: refs/heads/master@{#653670}

content/browser/tracing/background_tracing_active_scenario.cc

@@ -142,12 +142,14 @@ void BackgroundTracingActiveScenario::StartTracing(
     config.SetTraceBufferSizeInEvents(20000);
     config.SetTraceBufferSizeInKb(500);
   }
-#endif
-
+#else
+  // TODO(crbug.com/941318): Re-enable startup tracing for Android once all
+  // Perfetto-related deadlocks are resolved.
   if (!TracingControllerImpl::GetInstance()->IsTracing() &&
       tracing::TracingUsesPerfettoBackend()) {
     tracing::TraceEventDataSource::GetInstance()->SetupStartupTracing();
   }
+#endif
 
   if (!TracingControllerImpl::GetInstance()->StartTracing(
           config,

content/browser/tracing/background_tracing_manager_browsertest.cc

@@ -17,6 +17,7 @@
 #include "base/strings/pattern.h"
 #include "base/task/post_task.h"
 #include "base/trace_event/trace_event.h"
+#include "build/build_config.h"
 #include "content/browser/tracing/background_startup_tracing_observer.h"
 #include "content/browser/tracing/background_tracing_active_scenario.h"
 #include "content/browser/tracing/background_tracing_manager_impl.h"
@@ -436,8 +437,15 @@ IN_PROC_BROWSER_TEST_F(BackgroundTracingManagerBrowserTest,
 // the full WaitForTracingEnabled() callback (background tracing will directly
 // enable the TraceLog so we get events prior to waiting for the whole IPC
 // sequence to enable tracing coming back from the tracing service).
+// Temporarily disabled startup tracing on Android to be able to unblock
+// Perfetto-based background tracing: https://crbug.com/941318
+#if defined(OS_ANDROID)
+#define MAYBE_EarlyTraceEventsInTrace DISABLED_EarlyTraceEventsInTrace
+#else
+#define MAYBE_EarlyTraceEventsInTrace EarlyTraceEventsInTrace
+#endif
 IN_PROC_BROWSER_TEST_F(BackgroundTracingManagerBrowserTest,
-                       EarlyTraceEventsInTrace) {
+                       MAYBE_EarlyTraceEventsInTrace) {
   TestTraceReceiverHelper trace_receiver_helper;
   TestBackgroundTracingHelper background_tracing_helper;