diff --git a/js/xpconnect/loader/mozJSComponentLoader.cpp b/js/xpconnect/loader/mozJSComponentLoader.cpp
index df7e96e0a2b..9428d817f0c 100644
--- a/js/xpconnect/loader/mozJSComponentLoader.cpp
+++ b/js/xpconnect/loader/mozJSComponentLoader.cpp
@@ -570,6 +570,37 @@ mozJSComponentLoader::NoteSubScript(HandleScript aScript, HandleObject aThisObje
   mThisObjects.Put(aScript, aThisObject);
 }
 
+/* static */ size_t
+mozJSComponentLoader::DataEntrySizeOfExcludingThis(const nsACString& aKey,
+                                                   ModuleEntry* const& aData,
+                                                   MallocSizeOf aMallocSizeOf, void*)
+{
+    return aKey.SizeOfExcludingThisIfUnshared(aMallocSizeOf) +
+        aData->SizeOfIncludingThis(aMallocSizeOf);
+}
+
+/* static */ size_t
+mozJSComponentLoader::ClassEntrySizeOfExcludingThis(const nsACString& aKey,
+                                                    const nsAutoPtr<ModuleEntry>& aData,
+                                                    MallocSizeOf aMallocSizeOf, void*)
+{
+    return aKey.SizeOfExcludingThisIfUnshared(aMallocSizeOf) +
+        aData->SizeOfIncludingThis(aMallocSizeOf);
+}
+
+size_t
+mozJSComponentLoader::SizeOfIncludingThis(MallocSizeOf aMallocSizeOf)
+{
+    size_t amount = aMallocSizeOf(this);
+
+    amount += mModules.SizeOfExcludingThis(DataEntrySizeOfExcludingThis, aMallocSizeOf);
+    amount += mImports.SizeOfExcludingThis(ClassEntrySizeOfExcludingThis, aMallocSizeOf);
+    amount += mInProgressImports.SizeOfExcludingThis(DataEntrySizeOfExcludingThis, aMallocSizeOf);
+    amount += mThisObjects.SizeOfExcludingThis(nullptr, aMallocSizeOf);
+
+    return amount;
+}
+
 // Some stack based classes for cleaning up on early return
 #ifdef HAVE_PR_MEMMAP
 class FileAutoCloser
@@ -1353,6 +1384,15 @@ mozJSComponentLoader::Observe(nsISupports *subject, const char *topic,
     return NS_OK;
 }
 
+size_t
+mozJSComponentLoader::ModuleEntry::SizeOfIncludingThis(MallocSizeOf aMallocSizeOf) const
+{
+    size_t n = aMallocSizeOf(this);
+    n += aMallocSizeOf(location);
+
+    return n;
+}
+
 /* static */ already_AddRefed<nsIFactory>
 mozJSComponentLoader::ModuleEntry::GetFactory(const mozilla::Module& module,
                                               const mozilla::Module::CIDEntry& entry)
diff --git a/js/xpconnect/loader/mozJSComponentLoader.h b/js/xpconnect/loader/mozJSComponentLoader.h
index 17781640e61..86d2207143d 100644
--- a/js/xpconnect/loader/mozJSComponentLoader.h
+++ b/js/xpconnect/loader/mozJSComponentLoader.h
@@ -7,6 +7,7 @@
 #ifndef mozJSComponentLoader_h
 #define mozJSComponentLoader_h
 
+#include "mozilla/MemoryReporting.h"
 #include "mozilla/ModuleLoader.h"
 #include "nsISupports.h"
 #include "nsIObserver.h"
@@ -55,6 +56,8 @@ class mozJSComponentLoader : public mozilla::ModuleLoader,
 
     void NoteSubScript(JS::HandleScript aScript, JS::HandleObject aThisObject);
 
+    size_t SizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf);
+
  protected:
     static mozJSComponentLoader* sSelf;
 
@@ -125,6 +128,8 @@ class mozJSComponentLoader : public mozilla::ModuleLoader,
             location = nullptr;
         }
 
+        size_t SizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf) const;
+
         static already_AddRefed<nsIFactory> GetFactory(const mozilla::Module& module,
                                                        const mozilla::Module::CIDEntry& entry);
 
@@ -135,6 +140,12 @@ class mozJSComponentLoader : public mozilla::ModuleLoader,
 
     friend class ModuleEntry;
 
+    static size_t DataEntrySizeOfExcludingThis(const nsACString& aKey, ModuleEntry* const& aData,
+                                               mozilla::MallocSizeOf aMallocSizeOf, void* arg);
+    static size_t ClassEntrySizeOfExcludingThis(const nsACString& aKey,
+                                                const nsAutoPtr<ModuleEntry>& aData,
+                                                mozilla::MallocSizeOf aMallocSizeOf, void* arg);
+
     // Modules are intentionally leaked, but still cleared.
     static PLDHashOperator ClearModules(const nsACString& key, ModuleEntry*& entry, void* cx);
     nsDataHashtable<nsCStringHashKey, ModuleEntry*> mModules;
diff --git a/js/xpconnect/src/XPCJSRuntime.cpp b/js/xpconnect/src/XPCJSRuntime.cpp
index 6802c6671d8..44ccf44baa0 100644
--- a/js/xpconnect/src/XPCJSRuntime.cpp
+++ b/js/xpconnect/src/XPCJSRuntime.cpp
@@ -14,6 +14,7 @@
 #include "XPCJSMemoryReporter.h"
 #include "WrapperFactory.h"
 #include "dom_quickstubs.h"
+#include "mozJSComponentLoader.h"
 
 #include "nsIMemoryReporter.h"
 #include "nsIObserverService.h"
@@ -2634,6 +2635,9 @@ JSReporter::CollectReports(WindowPaths *windowPaths,
 
     size_t scopes = XPCWrappedNativeScope::SizeOfAllScopesIncludingThis(JSMallocSizeOf);
 
+    mozJSComponentLoader* loader = mozJSComponentLoader::Get();
+    size_t jsComponentLoaderSize = loader ? loader->SizeOfIncludingThis(JSMallocSizeOf) : 0;
+
     // This is the second step (see above).  First we report stuff in the
     // "explicit" tree, then we report other stuff.
 
@@ -2723,6 +2727,10 @@ JSReporter::CollectReports(WindowPaths *windowPaths,
                  KIND_HEAP, scopes,
                  "Memory used by XPConnect scopes.");
 
+    REPORT_BYTES(NS_LITERAL_CSTRING("explicit/xpconnect/js-component-loader"),
+                 KIND_HEAP, jsComponentLoaderSize,
+                 "Memory used by XPConnect's JS component loader.");
+
     return NS_OK;
 }