Investigate & fix issues around usage_count and deoptimization_count

runtime/vm/weak_code.cc

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/weak_code.h"
 
 #include "platform/assert.h"
 
 #include "vm/code_generator.h"
 #include "vm/code_patcher.h"
 #include "vm/compiler.h"
 #include "vm/object.h"
 #include "vm/stack_frame.h"
 
 namespace dart {
 
+bool WeakCodeReferences::HasCodes() const {
+  return !array_.IsNull() && (array_.Length() > 0);
+}
+
+
 void WeakCodeReferences::Register(const Code& value) {
   if (!array_.IsNull()) {
     // Try to find and reuse cleared WeakProperty to avoid allocating new one.
     WeakProperty& weak_property = WeakProperty::Handle();
     for (intptr_t i = 0; i < array_.Length(); i++) {
       weak_property ^= array_.At(i);
       if (weak_property.key() == Code::null()) {
         // Empty property found. Reuse it.
         weak_property.set_key(value);
         return;
@@ skipping 97 matching lines @@
       // Make non-OSR code non-entrant.
       if (!code.IsDisabled()) {
         ReportSwitchingCode(code);
         code.DisableDartCode();
       }
     }
   }
 }
 
 }  // namespace dart