Bug 1805996 - Implement scaffolding for a memory reporter in FOG r=chutten

This is a minimal implementation, which does not measure any of the
Glean-internal/metric memory usage yet.

Differential Revision: https://phabricator.services.mozilla.com/D207137

toolkit/components/glean/xpcom/FOG.cpp

@@ -65,6 +65,7 @@ already_AddRefed<FOG> FOG::GetSingleton() {
   MOZ_LOG(sLog, LogLevel::Debug, ("FOG::GetSingleton()"));
 
   gFOG = new FOG();
+  gFOG->InitMemoryReporter();
 
   if (XRE_IsParentProcess()) {
     nsresult rv;
@@ -106,6 +107,8 @@ already_AddRefed<FOG> FOG::GetSingleton() {
 
 void FOG::Shutdown() {
   MOZ_ASSERT(XRE_IsParentProcess());
+
+  UnregisterWeakMemoryReporter(this);
   glean::impl::fog_shutdown();
 }
 
@@ -421,6 +424,22 @@ FOG::TestRegisterRuntimePing(
   return NS_OK;
 }
 
+void FOG::InitMemoryReporter() { RegisterWeakMemoryReporter(this); }
+
+MOZ_DEFINE_MALLOC_SIZE_OF(FOGMallocSizeOf)
+
+NS_IMETHODIMP
+FOG::CollectReports(nsIHandleReportCallback* aHandleReport, nsISupports* aData,
+                    bool aAnonymize) {
+  mozilla::MallocSizeOf aMallocSizeOf = FOGMallocSizeOf;
+
+  MOZ_COLLECT_REPORT("explicit/fog/impl", KIND_HEAP, UNITS_BYTES,
+                     aMallocSizeOf(this),
+                     "Memory used by the FOG core implementation");
+
+  return NS_OK;
+}
+
 NS_IMPL_ISUPPORTS(FOG, nsIFOG, nsIObserver)
 
 }  //  namespace mozilla

toolkit/components/glean/xpcom/FOG.h

@@ -8,16 +8,19 @@
 
 #include "nsIFOG.h"
 #include "nsIObserver.h"
+#include "nsIMemoryReporter.h"
 
 namespace mozilla {
-class FOG final : public nsIFOG, public nsIObserver {
+class FOG final : public nsIFOG, public nsIObserver, public nsIMemoryReporter {
   NS_DECL_THREADSAFE_ISUPPORTS
   NS_DECL_NSIFOG
   NS_DECL_NSIOBSERVER
+  NS_DECL_NSIMEMORYREPORTER
 
  public:
   FOG() = default;
   static already_AddRefed<FOG> GetSingleton();
+  void InitMemoryReporter();
 
  private:
   ~FOG() = default;