A speculative Revert for r165872 - Remove static thread pointers from CC, attempt 2

cc/single_thread_proxy.h

Index: cc/single_thread_proxy.h
===================================================================
--- cc/single_thread_proxy.h	(revision 165906)
+++ cc/single_thread_proxy.h	(working copy)
@@ -91,58 +91,42 @@
 // code is running on the impl thread to satisfy assertion checks.
 class DebugScopedSetImplThread {
 public:
-    explicit DebugScopedSetImplThread(Proxy* proxy)
-        : m_proxy(proxy)
+    DebugScopedSetImplThread()
     {
 #ifndef NDEBUG
-        m_previousValue = m_proxy->m_implThreadIsOverridden;
-        m_proxy->setCurrentThreadIsImplThread(true);
+        Proxy::setCurrentThreadIsImplThread(true);
 #endif
     }
     ~DebugScopedSetImplThread()
     {
 #ifndef NDEBUG
-        m_proxy->setCurrentThreadIsImplThread(m_previousValue);
+        Proxy::setCurrentThreadIsImplThread(false);
 #endif
     }
-private:
-    bool m_previousValue;
-    Proxy* m_proxy;
 };
 
 // For use in the single-threaded case. In debug builds, it pretends that the
 // code is running on the main thread to satisfy assertion checks.
 class DebugScopedSetMainThread {
 public:
-    explicit DebugScopedSetMainThread(Proxy* proxy)
-        : m_proxy(proxy)
+    DebugScopedSetMainThread()
     {
 #ifndef NDEBUG
-        m_previousValue = m_proxy->m_implThreadIsOverridden;
-        m_proxy->setCurrentThreadIsImplThread(false);
+        Proxy::setCurrentThreadIsImplThread(false);
 #endif
     }
     ~DebugScopedSetMainThread()
     {
 #ifndef NDEBUG
-        m_proxy->setCurrentThreadIsImplThread(m_previousValue);
+        Proxy::setCurrentThreadIsImplThread(true);
 #endif
     }
-private:
-    bool m_previousValue;
-    Proxy* m_proxy;
 };
 
 // For use in the single-threaded case. In debug builds, it pretends that the
 // code is running on the impl thread and that the main thread is blocked to
 // satisfy assertion checks
 class DebugScopedSetImplThreadAndMainThreadBlocked {
-public:
-    explicit DebugScopedSetImplThreadAndMainThreadBlocked(Proxy* proxy)
-        : m_implThread(proxy)
-        , m_mainThreadBlocked(proxy)
-    {
-    }
 private:
     DebugScopedSetImplThread m_implThread;
     DebugScopedSetMainThreadBlocked m_mainThreadBlocked;