Bug 1919511 - Rename gfxFontGroup::BuildFontList to EnsureFontList, and defer calling it until we really need the resolved font instances. r=layout-reviewers,emilio

This is preparation for splitting out separate per-script resolved font lists in gfxFontGroup.
By itself, it should not change behavior.

Differential Revision: https://phabricator.services.mozilla.com/D222748

layout/generic/nsTextFrame.cpp

@@ -2385,14 +2385,7 @@ already_AddRefed<gfxTextRun> BuildTextRunsScanner::BuildTextRunForFrames(
     fontInflation = nsLayoutUtils::FontSizeInflationFor(firstFrame);
     fontGroup = GetInflatedFontGroupForFrame(firstFrame);
   }
-
-  if (fontGroup) {
-    // Refresh fontgroup if necessary, before trying to build textruns.
-    fontGroup->CheckForUpdatedPlatformList();
-  } else {
-    DestroyUserData(userDataToDestroy);
-    return nullptr;
-  }
+  MOZ_ASSERT(fontGroup);
 
   if (flags2 & nsTextFrameUtils::Flags::HasTab) {
     flags |= gfx::ShapedTextFlags::TEXT_ENABLE_SPACING;