[RegisterConfiguration] Streamline access to arch defaults, simplify Registers.

src/frames.cc

Index: src/frames.cc
diff --git a/src/frames.cc b/src/frames.cc
index 20776f6b1b37613ecfc1637b737677b500ccebe7..698b93541f581beb57497377d1fc2c4c12b6a455 100644
--- a/src/frames.cc
+++ b/src/frames.cc
@@ -728,10 +728,9 @@ void StandardFrame::IterateCompiledFrame(ObjectVisitor* v) const {
   if (safepoint_entry.has_doubles()) {
     // Number of doubles not known at snapshot time.
     DCHECK(!isolate()->serializer_enabled());
-    parameters_base +=
-        RegisterConfiguration::ArchDefault(RegisterConfiguration::CRANKSHAFT)
-            ->num_allocatable_double_registers() *
-        kDoubleSize / kPointerSize;
+    parameters_base += RegisterConfiguration::Crankshaft()
+                           ->num_allocatable_double_registers() *
+                       kDoubleSize / kPointerSize;
   }
 
   // Visit the registers that contain pointers if any.