Remove `pragma optimize` from v8.

This instance of `pragma optimize` was from long ago when we built with
frame pointers disabled. We always build with frame pointers on these
days.

(Also, clang-cl ignores this pragma and will warn about it.)

Bug: chromium:505314
Change-Id: Ia125c9c54e6ec486247241102de1cb62c72d268b
Reviewed-on: https://chromium-review.googlesource.com/993423
Commit-Queue: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52336}

src/base/debug/stack_trace_win.cc

@@ -163,24 +163,11 @@ void DisableSignalStackDump() {
   g_dump_stack_in_signal_handler = false;
 }
 
-// Disable optimizations for the StackTrace::StackTrace function. It is
-// important to disable at least frame pointer optimization ("y"), since
-// that breaks CaptureStackBackTrace() and prevents StackTrace from working
-// in Release builds (it may still be janky if other frames are using FPO,
-// but at least it will make it further).
-#if defined(V8_CC_MSVC)
-#pragma optimize("", off)
-#endif
-
 StackTrace::StackTrace() {
   // When walking our own stack, use CaptureStackBackTrace().
   count_ = CaptureStackBackTrace(0, arraysize(trace_), trace_, nullptr);
 }
 
-#if defined(V8_CC_MSVC)
-#pragma optimize("", on)
-#endif
-
 StackTrace::StackTrace(EXCEPTION_POINTERS* exception_pointers) {
   InitTrace(exception_pointers->ContextRecord);
 }