[ObjC ARC] Converts ios/chrome/browser/passwords:unit_tests to ARC.

ios/web/public/test/test_web_state.mm

Index: ios/web/public/test/test_web_state.mm
diff --git a/ios/web/public/test/test_web_state.mm b/ios/web/public/test/test_web_state.mm
index 3906434aad0d174b0b23fe0a9107ab3f534dcc77..3d35c1f7abdc2ec3507677c20a0759967d431967 100644
--- a/ios/web/public/test/test_web_state.mm
+++ b/ios/web/public/test/test_web_state.mm
@@ -7,16 +7,30 @@
 #include <stdint.h>
 
 #include "base/callback.h"
+#include "ios/web/public/web_state/web_state_observer.h"
 
 namespace web {
 
+void TestWebState::AddObserver(WebStateObserver* observer) {
+  observers_.AddObserver(observer);
+}
+
+void TestWebState::RemoveObserver(WebStateObserver* observer) {
+  observers_.RemoveObserver(observer);
+}
+
 TestWebState::TestWebState()
     : web_usage_enabled_(false),
       is_loading_(false),
       trust_level_(kAbsolute),
       content_is_html_(true) {}
 
-TestWebState::~TestWebState() = default;
+TestWebState::~TestWebState() {
+  for (auto& observer : observers_)
+    observer.WebStateDestroyed();
+  for (auto& observer : observers_)
+    observer.ResetWebState();
+};
 
 WebStateDelegate* TestWebState::GetDelegate() {
   return nil;