virtual destructor in exec_ctx, remove unneeded flush in grpc_shutdown and remove grpc_exec_ctx from .pxi files in python

src/core/ext/filters/client_channel/lb_policy.cc

@@ -130,7 +130,7 @@ void grpc_lb_policy_exit_idle_locked(grpc_lb_policy* policy) {
 void grpc_lb_policy_ping_one_locked(grpc_lb_policy* policy,
                                     grpc_closure* on_initiate,
                                     grpc_closure* on_ack) {
-  policy->vtable->ping_one_locked(exec_ctx, policy, on_initiate, on_ack);
+  policy->vtable->ping_one_locked(policy, on_initiate, on_ack);
 }
 
 void grpc_lb_policy_notify_on_state_change_locked(

src/core/lib/iomgr/exec_ctx.h

@@ -80,7 +80,7 @@ class ExecCtx {
   ExecCtx(uintptr_t fl) : flags_(fl) { Set(this); }
 
   /** Destructor */
-  ~ExecCtx() {
+  virtual ~ExecCtx() {
     flags_ |= GRPC_EXEC_CTX_FLAG_IS_FINISHED;
     Flush();
     Set(last_exec_ctx_);

src/core/lib/surface/init.cc

@@ -157,9 +157,6 @@ void grpc_init(void) {
 void grpc_shutdown(void) {
   int i;
   GRPC_API_TRACE("grpc_shutdown(void)", 0, ());
-  if (grpc_core::ExecCtx::Get()) {
-    grpc_core::ExecCtx::Get()->Flush();
-  }
   gpr_mu_lock(&g_init_mu);
   if (--g_initializations == 0) {
     {

src/python/grpcio/grpc/_cython/_cygrpc/grpc.pxi

@@ -36,13 +36,6 @@ cdef extern from "grpc/byte_buffer_reader.h":
     pass
 
 
-cdef extern from "grpc/impl/codegen/exec_ctx_fwd.h":
-
-  struct grpc_exec_ctx:
-    # We don't care about the internals
-    pass
-
-
 cdef extern from "grpc/grpc.h":
 
   ctypedef struct grpc_slice:
@@ -169,7 +162,7 @@ cdef extern from "grpc/grpc.h":
 
   ctypedef struct grpc_arg_pointer_vtable:
     void *(*copy)(void *)
-    void (*destroy)(grpc_exec_ctx *, void *)
+    void (*destroy)(void *)
     int (*cmp)(void *, void *)
 
   ctypedef struct grpc_arg_value_pointer:

src/python/grpcio/grpc/_cython/_cygrpc/records.pyx.pxi

@@ -320,7 +320,7 @@ cdef void* copy_ptr(void* ptr):
   return ptr
 
 
-cdef void destroy_ptr(grpc_exec_ctx* ctx, void* ptr):
+cdef void destroy_ptr(void* ptr):
   pass