Fix more -Wsign-compare warnings in heap, mips, base, etc.

src/cancelable-task.cc

 // Copyright 2015 the V8 project 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 "src/cancelable-task.h"
 
 #include "src/base/platform/platform.h"
 #include "src/isolate.h"
 
 namespace v8 {
@@ skipping 26 matching lines @@
   CHECK(!canceled_);
   cancelable_tasks_[id] = task;
   return id;
 }
 
 
 void CancelableTaskManager::RemoveFinishedTask(uint32_t id) {
   base::LockGuard<base::Mutex> guard(&mutex_);
   size_t removed = cancelable_tasks_.erase(id);
   USE(removed);
-  DCHECK_NE(0, removed);
+  DCHECK_NE(0u, removed);
   cancelable_tasks_barrier_.NotifyOne();
 }
 
 CancelableTaskManager::TryAbortResult CancelableTaskManager::TryAbort(
     uint32_t id) {
   base::LockGuard<base::Mutex> guard(&mutex_);
   auto entry = cancelable_tasks_.find(id);
   if (entry != cancelable_tasks_.end()) {
     Cancelable* value = entry->second;
     if (value->Cancel()) {
@@ skipping 38 matching lines @@
 
 CancelableTask::CancelableTask(Isolate* isolate)
     : Cancelable(isolate->cancelable_task_manager()), isolate_(isolate) {}
 
 
 CancelableIdleTask::CancelableIdleTask(Isolate* isolate)
     : Cancelable(isolate->cancelable_task_manager()), isolate_(isolate) {}
 
 }  // namespace internal
 }  // namespace v8