PPAPI: Make TrackedCallback more threadsafe

ppapi/shared_impl/proxy_lock.h

Index: ppapi/shared_impl/proxy_lock.h
diff --git a/ppapi/shared_impl/proxy_lock.h b/ppapi/shared_impl/proxy_lock.h
index 39b653e1a00bccb49217f9b494d4d5a666d5a67d..32728bd8e9ab19f52041e2f6d94a9db621b957ff 100644
--- a/ppapi/shared_impl/proxy_lock.h
+++ b/ppapi/shared_impl/proxy_lock.h
@@ -175,9 +175,6 @@ class RunWhileLockedHelper<void()> {
   typedef base::Callback<void()> CallbackType;
   explicit RunWhileLockedHelper(const CallbackType& callback)
       : callback_(new CallbackType(callback)) {
-    // Copying |callback| may adjust reference counts for bound Vars or
-    // Resources; we should have the lock already.
-    ProxyLock::AssertAcquired();
     // CallWhileLocked and destruction might happen on a different thread from
     // creation.
     thread_checker_.DetachFromThread();
@@ -238,7 +235,6 @@ class RunWhileLockedHelper<void(P1)> {
   typedef base::Callback<void(P1)> CallbackType;
   explicit RunWhileLockedHelper(const CallbackType& callback)
       : callback_(new CallbackType(callback)) {
-    ProxyLock::AssertAcquired();
     thread_checker_.DetachFromThread();
   }
   void CallWhileLocked(P1 p1) {
@@ -268,7 +264,6 @@ class RunWhileLockedHelper<void(P1, P2)> {
   typedef base::Callback<void(P1, P2)> CallbackType;
   explicit RunWhileLockedHelper(const CallbackType& callback)
       : callback_(new CallbackType(callback)) {
-    ProxyLock::AssertAcquired();
     thread_checker_.DetachFromThread();
   }
   void CallWhileLocked(P1 p1, P2 p2) {
@@ -298,7 +293,6 @@ class RunWhileLockedHelper<void(P1, P2, P3)> {
   typedef base::Callback<void(P1, P2, P3)> CallbackType;
   explicit RunWhileLockedHelper(const CallbackType& callback)
       : callback_(new CallbackType(callback)) {
-    ProxyLock::AssertAcquired();
     thread_checker_.DetachFromThread();
   }
   void CallWhileLocked(P1 p1, P2 p2, P3 p3) {