Fix "unused variable" warnings.

gin/wrappable_unittest.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/logging.h"
 #include "base/macros.h"
 #include "gin/arguments.h"
 #include "gin/handle.h"
 #include "gin/object_template_builder.h"
 #include "gin/per_isolate_data.h"
 #include "gin/public/isolate_holder.h"
 #include "gin/test/v8_test.h"
 #include "gin/try_catch.h"
 #include "gin/wrappable.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace gin {
 
+// This useless base class ensures that the value of a pointer to a MyObject
+// (below) is not the same as the value of that pointer cast to the object's
+// WrappableBase base.
 class BaseClass {
  public:
   BaseClass() : value_(23) {}
   virtual ~BaseClass() {}
 
+  // So the compiler doesn't complain that |value_| is unused.
+  int value() const { return value_; }
+
  private:
   int value_;
 
   DISALLOW_COPY_AND_ASSIGN(BaseClass);
 };
 
 class MyObject : public BaseClass,
                  public Wrappable<MyObject> {
  public:
   static WrapperInfo kWrapperInfo;
@@ skipping 166 matching lines @@
   v8::Local<v8::Function> func;
   EXPECT_TRUE(ConvertFromV8(isolate, val, &func));
   v8::Local<v8::Value> argv[] = {
     ConvertToV8(isolate, object.get())
   };
   func->Call(v8::Undefined(isolate), 1, argv);
   EXPECT_TRUE(try_catch.HasCaught());
 }
 
 }  // namespace gin