Fixed problem where AndroidShellHolder was trashing the ThreadHost in its deconstructor (flutter#24644)

Author: gaaclarke

shell/common/thread_host.cc

@@ -35,12 +35,4 @@ ThreadHost::ThreadHost(std::string name_prefix_arg, uint64_t mask)
 
 ThreadHost::~ThreadHost() = default;
 
-void ThreadHost::Reset() {
-  platform_thread.reset();
-  ui_thread.reset();
-  raster_thread.reset();
-  io_thread.reset();
-  profiler_thread.reset();
-}
-
 }  // namespace flutter

shell/common/thread_host.h

@@ -38,8 +38,6 @@ struct ThreadHost {
   ThreadHost(std::string name_prefix, uint64_t type_mask);
 
   ~ThreadHost();
-
-  void Reset();
 };
 
 }  // namespace flutter

shell/platform/android/android_shell_holder.cc

@@ -170,7 +170,7 @@ AndroidShellHolder::AndroidShellHolder(
 
 AndroidShellHolder::~AndroidShellHolder() {
   shell_.reset();
-  thread_host_->Reset();
+  thread_host_.reset();
 }
 
 bool AndroidShellHolder::IsValid() const {