Bug 1405105 - remove Rust init hack now that we require 1.19; r=ccorcoran

We added this to avoid race conditions, but a fix which removes the need
for it has been landed in Rust 1.19+, which we now require.

toolkit/library/rust/shared/lib.rs

@@ -30,14 +30,6 @@ use std::panic;
 
 
 
-// This workaround is fixed in Rust 1.19. For details, see bug 1358151.
-thread_local!(static UNUSED_THREAD_LOCAL: () = ());
-#[no_mangle]
-pub extern "C" fn rust_init_please_remove_this_after_updating_rust_1_19() {
-    UNUSED_THREAD_LOCAL.with(|_| ());
-}
-
-
 /// Used to implement `nsIDebug2::RustPanic` for testing purposes.
 #[no_mangle]
 pub extern "C" fn intentional_panic(message: *const c_char) {

toolkit/xre/nsAppRunner.cpp

@@ -231,12 +231,6 @@
 extern uint32_t gRestartMode;
 extern void InstallSignalHandlers(const char *ProgramName);
 
-// This workaround is fixed in Rust 1.19. For details, see bug 1358151.
-// Implementation in toolkit/library/rust/shared/lib.rs
-extern "C" {
-  void rust_init_please_remove_this_after_updating_rust_1_19();
-}
-
 #define FILE_COMPATIBILITY_INFO NS_LITERAL_CSTRING("compatibility.ini")
 #define FILE_INVALIDATE_CACHES NS_LITERAL_CSTRING(".purgecaches")
 
@@ -3200,9 +3194,6 @@ XREMain::XRE_mainInit(bool* aExitFlag)
     return 1;
   *aExitFlag = false;
 
-  // This workaround is fixed in Rust 1.19. For details, see bug 1358151.
-  rust_init_please_remove_this_after_updating_rust_1_19();
-
   atexit(UnexpectedExit);
   auto expectedShutdown = mozilla::MakeScopeExit([&] {
     MozExpectedExit();