Write protect executable pages in the VM.

runtime/vm/assembler_ia32.h

Index: runtime/vm/assembler_ia32.h
diff --git a/runtime/vm/assembler_ia32.h b/runtime/vm/assembler_ia32.h
index 37d4b9c0ebf51a2be023a7e7bb4f82d719086a20..a5470c6472d01ffc7b515ebb2ffbf12d9253d061 100644
--- a/runtime/vm/assembler_ia32.h
+++ b/runtime/vm/assembler_ia32.h
@@ -708,6 +708,12 @@ class Assembler : public ValueObject {
 
   intptr_t CodeSize() const { return buffer_.Size(); }
   intptr_t prologue_offset() const { return prologue_offset_; }
+
+  // Count the fixups that produce a pointer offset, without processing
+  // the fixups.
+  intptr_t CountPointerOffsets() const {
+    return buffer_.CountPointerOffsets();
+  }
   const ZoneGrowableArray<intptr_t>& GetPointerOffsets() const {
     return buffer_.pointer_offsets();
   }