Bug 1520238 - Measure memory by default when MOZ_PROFILER_STARTUP is set - r=mstange

Differential Revision: https://phabricator.services.mozilla.com/D25712

--HG--
extra : moz-landing-system : lando

tools/profiler/core/platform.cpp

@@ -239,7 +239,7 @@ static uint32_t DefaultFeatures() {
 static uint32_t StartupExtraDefaultFeatures() {
   // Enable mainthreadio by default for startup profiles as startup is heavy on
   // I/O operations, and main thread I/O is really important to see there.
-  return ProfilerFeature::MainThreadIO;
+  return ProfilerFeature::MainThreadIO | ProfilerFeature::Memory;
 }
 
 class PSMutex : public StaticMutex {};