Setup R10/EDX to be valid Oops before stub calls

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 854afd0481ffe9a8a207103d41183ede06d6504d..160bf3c085db2e03bdc6984ffef9578bd8b404eb 100644
--- a/runtime/vm/runtime_entry_ia32.cc
+++ b/runtime/vm/runtime_entry_ia32.cc
@@ -20,7 +20,7 @@ namespace dart {
 // For regular runtime calls -
 //   ESP : points to the arguments and return value array.
 //   ECX : address of the runtime function to call.
-//   EDX : number of arguments to the call.
+//   EDX : number of arguments to the call as Smi.
 // For leaf calls the caller is responsible to setup the arguments
 // and look for return values based on the C calling convention.
 void RuntimeEntry::Call(Assembler* assembler, intptr_t argument_count) const {
@@ -32,7 +32,7 @@ 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.
     __ movl(ECX, Immediate(GetEntryPoint()));
-    __ movl(EDX, Immediate(argument_count));
+    __ movl(EDX, Immediate(Smi::RawValue(argument_count)));
     __ call(&StubCode::CallToRuntimeLabel());
   }
 }