Specialize breakpoint stubs by set of live registers of the stubs they are intercepting.

runtime/vm/runtime_entry_ia32.cc

Index: runtime/vm/runtime_entry_ia32.cc
diff --git a/runtime/vm/runtime_entry_ia32.cc b/runtime/vm/runtime_entry_ia32.cc
index 160bf3c085db2e03bdc6984ffef9578bd8b404eb..f8a1433931c6d25685bfcbc75eeaa35296291b16 100644
--- a/runtime/vm/runtime_entry_ia32.cc
+++ b/runtime/vm/runtime_entry_ia32.cc
@@ -31,8 +31,9 @@ void RuntimeEntry::Call(Assembler* assembler, intptr_t argument_count) const {
   } else {
     // Argument count is not checked here, but in the runtime entry for a more
     // informative error message.
+    ASSERT((GetEntryPoint() & kSmiTagMask) == 0);
     __ movl(ECX, Immediate(GetEntryPoint()));
-    __ movl(EDX, Immediate(Smi::RawValue(argument_count)));
+    __ movl(EDX, Immediate(argument_count));
     __ call(&StubCode::CallToRuntimeLabel());
   }
 }