[ARC] Converts part of ios/web/ui to ARC.

ios/web/web_state/js/crw_js_injection_manager.mm

Index: ios/web/web_state/js/crw_js_injection_manager.mm
diff --git a/ios/web/web_state/js/crw_js_injection_manager.mm b/ios/web/web_state/js/crw_js_injection_manager.mm
index 416712668433d98a721e39911f878b497f071e49..9ef0c7eb6695f9c4c402f3f7bac8b4c7567cb2b9 100644
--- a/ios/web/web_state/js/crw_js_injection_manager.mm
+++ b/ios/web/web_state/js/crw_js_injection_manager.mm
@@ -13,12 +13,16 @@
 #import "ios/web/public/web_state/js/crw_js_injection_receiver.h"
 #import "ios/web/web_state/js/page_script_util.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 @implementation CRWJSInjectionManager {
   // JS to inject into the page. This may be nil if it has been purged due to
   // low memory.
   base::scoped_nsobject<NSString> _injectObject;
   // An object the can receive JavaScript injection.
-  CRWJSInjectionReceiver* _receiver;  // Weak.
+  __weak CRWJSInjectionReceiver* _receiver;
 }
 
 - (id)initWithReceiver:(CRWJSInjectionReceiver*)receiver {
@@ -38,7 +42,6 @@
 
 - (void)dealloc {
   [[NSNotificationCenter defaultCenter] removeObserver:self];
-  [super dealloc];
 }
 
 - (BOOL)hasBeenInjected {