Add asserts to ensure that we:

src/x64/regexp-macro-assembler-x64.cc

Index: src/x64/regexp-macro-assembler-x64.cc
===================================================================
--- src/x64/regexp-macro-assembler-x64.cc	(revision 9277)
+++ src/x64/regexp-macro-assembler-x64.cc	(working copy)
@@ -431,10 +431,15 @@
     // Isolate.
     __ LoadAddress(rcx, ExternalReference::isolate_address());
 #endif
-    ExternalReference compare =
-        ExternalReference::re_case_insensitive_compare_uc16(masm_.isolate());
-    __ CallCFunction(compare, num_arguments);
 
+    { // NOLINT: Can't find a way to open this scope without confusing the
+      // linter.
+      AllowExternalCallThatCantCauseGC scope(&masm_);
+      ExternalReference compare =
+          ExternalReference::re_case_insensitive_compare_uc16(masm_.isolate());
+      __ CallCFunction(compare, num_arguments);
+    }
+
     // Restore original values before reacting on result value.
     __ Move(code_object_pointer(), masm_.CodeObject());
     __ pop(backtrack_stackpointer());
@@ -706,7 +711,12 @@
   // registers we need.
   // Entry code:
   __ bind(&entry_label_);
-  // Start new stack frame.
+
+  // Tell the system that we have a stack frame.  Because the type is MANUAL, no
+  // is generated.
+  FrameScope scope(&masm_, StackFrame::MANUAL);
+
+  // Actually emit code to start a new stack frame.
   __ push(rbp);
   __ movq(rbp, rsp);
   // Save parameters and callee-save registers. Order here should correspond