Simplify constant pool usage in x64 code generator (by removing extra argument

runtime/vm/runtime_entry_x64.cc

Index: runtime/vm/runtime_entry_x64.cc
diff --git a/runtime/vm/runtime_entry_x64.cc b/runtime/vm/runtime_entry_x64.cc
index 0e3cbc69a1768b3baa9116971ddf7f99ef693e6a..fe342dc0b1ab2261f5178cc24c0962c28f73b2f3 100644
--- a/runtime/vm/runtime_entry_x64.cc
+++ b/runtime/vm/runtime_entry_x64.cc
@@ -29,9 +29,9 @@ void RuntimeEntry::Call(Assembler* assembler, intptr_t argument_count) const {
     // Argument count is not checked here, but in the runtime entry for a more
     // informative error message.
     ExternalLabel label(GetEntryPoint());
-    __ LoadExternalLabel(RBX, &label, kNotPatchable, PP);
+    __ LoadExternalLabel(RBX, &label, kNotPatchable);
     __ movq(R10, Immediate(argument_count));
-    __ Call(&StubCode::CallToRuntimeLabel(), PP);
+    __ Call(&StubCode::CallToRuntimeLabel());
   }
 }