Drop IsPregenerated() and allow_stub_calls flag.

src/code-stubs-hydrogen.cc

Index: src/code-stubs-hydrogen.cc
diff --git a/src/code-stubs-hydrogen.cc b/src/code-stubs-hydrogen.cc
index f717d75c192423425453b25f4da792b281e83662..03b8c18fbdae004a0c550fe0c515aa979569c397 100644
--- a/src/code-stubs-hydrogen.cc
+++ b/src/code-stubs-hydrogen.cc
@@ -251,9 +251,6 @@ Handle<Code> HydrogenCodeStub::GenerateLightweightMissCode(Isolate* isolate) {
     // Update the static counter each time a new code stub is generated.
     isolate->counters()->code_stubs()->Increment();
 
-    // Nested stubs are not allowed for leaves.
-    AllowStubCallsScope allow_scope(&masm, false);
-
     // Generate the code for the stub.
     masm.set_generating_stub(true);
     NoCurrentFrameScope scope(&masm);