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

ios/web/web_state/js/crw_js_window_id_manager.mm

Index: ios/web/web_state/js/crw_js_window_id_manager.mm
diff --git a/ios/web/web_state/js/crw_js_window_id_manager.mm b/ios/web/web_state/js/crw_js_window_id_manager.mm
index 8a4b0dc1accd727e015ce3f372c8a2a4c554c03e..2832a46cdd18b8e60998c2027360258d2b2dbefe 100644
--- a/ios/web/web_state/js/crw_js_window_id_manager.mm
+++ b/ios/web/web_state/js/crw_js_window_id_manager.mm
@@ -4,13 +4,16 @@
 
 #import "ios/web/web_state/js/crw_js_window_id_manager.h"
 
-#import "base/ios/weak_nsobject.h"
 #import "base/mac/scoped_nsobject.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/sys_string_conversions.h"
 #include "crypto/random.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
+
 namespace {
 // Number of random bytes in unique key for window ID. The length of the
 // window ID will be twice this number, as it is hexadecimal encoded.
@@ -37,7 +40,7 @@ const size_t kUniqueKeyLength = 16;
 
 - (instancetype)initWithWebView:(WKWebView*)webView {
   if ((self = [super init])) {
-    _webView.reset([webView retain]);
+    _webView.reset(webView);
     _windowID.reset([[self class] newUniqueKey]);
   }
   return self;
@@ -54,7 +57,7 @@ const size_t kUniqueKeyLength = 16;
       stringWithFormat:@"if (!window.__gCrWeb) {false; } else { %@; true; }",
                        script];
 
-  base::WeakNSObject<CRWJSWindowIDManager> weakSelf(self);
+  __weak CRWJSWindowIDManager* weakSelf = self;
   [_webView evaluateJavaScript:scriptWithResult
              completionHandler:^(id result, NSError* error) {
                if (error) {
@@ -63,7 +66,8 @@ const size_t kUniqueKeyLength = 16;
                  return;
                }
 
-               DCHECK_EQ(CFBooleanGetTypeID(), CFGetTypeID(result));
+               DCHECK_EQ(CFBooleanGetTypeID(),
+                         CFGetTypeID((__bridge CFTypeRef)result));
                if (![result boolValue]) {
                  // WKUserScript has not been injected yet. Retry window id
                  // injection, because it is critical for the system to
@@ -79,7 +83,7 @@ const size_t kUniqueKeyLength = 16;
   char randomBytes[kUniqueKeyLength];
   crypto::RandBytes(randomBytes, kUniqueKeyLength);
   std::string result = base::HexEncode(randomBytes, kUniqueKeyLength);
-  return [base::SysUTF8ToNSString(result) retain];
+  return base::SysUTF8ToNSString(result);
 }
 
 @end