Reenable extra_warnings config for angle_utils

Originally disabled in https://crrev.com/c/1738438.

Bug: angleproject:1459
Change-Id: I95172dc95a5d3e9d838c542ee6bcfb2338ffc9a6
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1743078
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>

BUILD.gn

@@ -1077,7 +1077,6 @@ foreach(is_shared_library,
     }
 
     configs += [ ":debug_annotations_config" ]
-    configs -= [ "${angle_root}:extra_warnings" ]
 
     public_configs += [ ":angle_util_config" ]
 

util/osx/OSXWindow.mm

@@ -12,6 +12,7 @@
 // Include Carbon to use the keycode names in Carbon's Event.h
 #include <Carbon/Carbon.h>
 
+#include "anglebase/no_destructor.h"
 #include "common/debug.h"
 
 // On OSX 10.12 a number of AppKit interfaces have been renamed for consistency, and the previous
@@ -23,7 +24,11 @@
 // Some events such as "ShouldTerminate" are sent to the whole application so we keep a list of
 // all the windows in order to forward the event to each of them. However this and calling pushEvent
 // in ApplicationDelegate is inherently unsafe in a multithreaded environment.
-static std::set<OSXWindow *> gAllWindows;
+static std::set<OSXWindow *> &AllWindows()
+{
+    static angle::base::NoDestructor<std::set<OSXWindow *>> allWindows;
+    return *allWindows;
+}
 
 @interface Application : NSApplication
 @end
@@ -33,7 +38,7 @@ - (void)sendEvent:(NSEvent *)nsEvent
 {
     if ([nsEvent type] == NSApplicationDefined)
     {
-        for (auto window : gAllWindows)
+        for (auto window : AllWindows())
         {
             if ([window->getNSWindow() windowNumber] == [nsEvent windowNumber])
             {
@@ -56,7 +61,7 @@ - (NSApplicationTerminateReply)applicationShouldTerminate:(NSApplication *)sende
 {
     Event event;
     event.Type = Event::EVENT_CLOSED;
-    for (auto window : gAllWindows)
+    for (auto window : AllWindows())
     {
         window->pushEvent(event);
     }
@@ -662,13 +667,13 @@ - (void)flagsChanged:(NSEvent *)nsEvent
     mWidth  = width;
     mHeight = height;
 
-    gAllWindows.insert(this);
+    AllWindows().insert(this);
     return true;
 }
 
 void OSXWindow::destroy()
 {
-    gAllWindows.erase(this);
+    AllWindows().erase(this);
 
     [mView release];
     mView = nil;