Fix some Windows compile issues.

mojo/edk/system/core_test_base.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 "mojo/edk/system/core_test_base.h"
 
 #include <vector>
 
 #include "base/compiler_specific.h"
 #include "base/logging.h"
@@ skipping 262 matching lines @@
 unsigned CoreTestBase_MockHandleInfo::GetRemoveAwakableCallCount() const {
   base::AutoLock locker(lock_);
   return remove_awakable_call_count_;
 }
 
 unsigned CoreTestBase_MockHandleInfo::GetCancelAllAwakablesCallCount() const {
   base::AutoLock locker(lock_);
   return cancel_all_awakables_call_count_;
 }
 
-unsigned CoreTestBase_MockHandleInfo::GetAddedAwakableSize() const {
+size_t CoreTestBase_MockHandleInfo::GetAddedAwakableSize() const {
   base::AutoLock locker(lock_);
   return added_awakables_.size();
 }
 
 Awakable* CoreTestBase_MockHandleInfo::GetAddedAwakableAt(unsigned i) const {
   base::AutoLock locker(lock_);
   return added_awakables_[i];
 }
 
 void CoreTestBase_MockHandleInfo::IncrementCtorCallCount() {
@@ skipping 77 matching lines @@
 }
 
 void CoreTestBase_MockHandleInfo::AwakableWasAdded(Awakable* awakable) {
   base::AutoLock locker(lock_);
   added_awakables_.push_back(awakable);
 }
 
 }  // namespace test
 }  // namespace system
 }  // namespace mojo