Bug 1584856 - patch 1 - Add some missing null-checks in dwrite font code. r=lsalzman

Differential Revision: https://phabricator.services.mozilla.com/D47788

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

gfx/thebes/gfxDWriteFontList.cpp

@@ -941,8 +941,14 @@ gfxFontEntry* gfxDWriteFontList::CreateFontEntry(
 #endif
   RefPtr<IDWriteFontFamily> family;
   collection->GetFontFamily(aFamily->Index(), getter_AddRefs(family));
+  if (!family) {
+    return nullptr;
+  }
   RefPtr<IDWriteFont> font;
   family->GetFont(aFace->mIndex, getter_AddRefs(font));
+  if (!font) {
+    return nullptr;
+  }
   nsAutoCString faceName;
   HRESULT hr = GetDirectWriteFontName(font, faceName);
   if (FAILED(hr)) {
@@ -1001,7 +1007,7 @@ void gfxDWriteFontList::GetFacesInitDataForFamily(
   for (unsigned i = 0; i < family->GetFontCount(); ++i) {
     RefPtr<IDWriteFont> dwFont;
     family->GetFont(i, getter_AddRefs(dwFont));
-    if (dwFont->GetSimulations() != DWRITE_FONT_SIMULATIONS_NONE) {
+    if (!dwFont || dwFont->GetSimulations() != DWRITE_FONT_SIMULATIONS_NONE) {
       continue;
     }
     DWRITE_FONT_STYLE dwstyle = dwFont->GetStyle();

gfx/thebes/gfxPlatformFontList.cpp

@@ -446,6 +446,9 @@ nsresult gfxPlatformFontList::InitFontList() {
   if (StaticPrefs::gfx_e10s_font_list_shared_AtStartup() &&
       !gfxPlatform::InSafeMode()) {
     for (auto i = mFontEntries.Iter(); !i.Done(); i.Next()) {
+      if (!i.Data()) {
+        continue;
+      }
       i.Data()->mShmemCharacterMap = nullptr;
       i.Data()->mShmemFace = nullptr;
       i.Data()->mFamilyName = NS_LITERAL_CSTRING("");