[Startup Tracing] Enable startup tracing from config file

content/app/android/library_loader_hooks.cc

Index: content/app/android/library_loader_hooks.cc
diff --git a/content/app/android/library_loader_hooks.cc b/content/app/android/library_loader_hooks.cc
index 66d71e2f7ef4817a40d015dd03d677be64a4d421..b801eb8bd688684d071d2257899f9e762cafeedf 100644
--- a/content/app/android/library_loader_hooks.cc
+++ b/content/app/android/library_loader_hooks.cc
@@ -16,6 +16,7 @@
 #include "base/strings/string_util.h"
 #include "base/trace_event/trace_event.h"
 #include "base/tracked_objects.h"
+#include "components/tracing/startup_tracing.h"
 #include "content/app/android/app_jni_registrar.h"
 #include "content/browser/android/browser_jni_registrar.h"
 #include "content/common/android/common_jni_registrar.h"
@@ -95,6 +96,8 @@ bool LibraryLoaded(JNIEnv* env, jclass clazz) {
         command_line->GetSwitchValueASCII(switches::kTraceStartup), "");
     base::trace_event::TraceLog::GetInstance()->SetEnabled(
         trace_config, base::trace_event::TraceLog::RECORDING_MODE);
+  } else {
+    tracing::EnableStartupTracingIfConfigFileExists();
   }
 
   // Android's main browser loop is custom so we set the browser