PlatformThreadHandle: remove public id() interface

base/threading/thread.h

Index: base/threading/thread.h
diff --git a/base/threading/thread.h b/base/threading/thread.h
index 5126491b3861cdb60f23eec1b40b11466d27a33a..f207dc1c1b5c05c30089501551cdb0803fc33413 100644
--- a/base/threading/thread.h
+++ b/base/threading/thread.h
@@ -118,7 +118,7 @@ class BASE_EXPORT Thread : PlatformThread::Delegate {
   // Blocks until the thread starts running. Called within StartAndWait().
   // Note that calling this causes jank on the calling thread, must be used
   // carefully for production code.
-  bool WaitUntilThreadStarted();
+  bool WaitUntilThreadStarted() const;
 
   // Signals the thread to exit and returns once the thread has exited.  After
   // this method returns, the Thread object is completely reset and may be used
@@ -170,7 +170,7 @@ class BASE_EXPORT Thread : PlatformThread::Delegate {
   // The native thread handle.
   PlatformThreadHandle thread_handle() { return thread_; }
 
-  // The thread ID.
+  // The thread ID. Should be called after one of Start*() is called.
   PlatformThreadId thread_id() const;
 
   // Returns true if the thread has been started, and not yet stopped.
@@ -212,15 +212,21 @@ class BASE_EXPORT Thread : PlatformThread::Delegate {
 
   // If true, we're in the middle of stopping, and shouldn't access
   // |message_loop_|. It may non-NULL and invalid.
+  // Should be written on the thread that creates this thread. Also read data
+  // could be wrong on other threads.
   bool stopping_;
 
   // True while inside of Run().
   bool running_;
-  mutable base::Lock running_lock_;  // Protects running_.
+
+  // Protects |running_|.
+  mutable base::Lock running_lock_;
 
   // The thread's handle.
   PlatformThreadHandle thread_;
-  mutable base::Lock thread_lock_;  // Protects thread_.
+
+  // The thread's id once it was started. Ensured by |start_event_|.
+  PlatformThreadId id_;
 
   // The thread's message loop.  Valid only while the thread is alive.  Set
   // by the created thread.