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

ios/chrome/browser/ui/history/favicon_view_provider_unittest.mm

Index: ios/chrome/browser/ui/history/favicon_view_provider_unittest.mm
diff --git a/ios/chrome/browser/ui/history/favicon_view_provider_unittest.mm b/ios/chrome/browser/ui/history/favicon_view_provider_unittest.mm
index 01faa948bdf4c77938f3ac112490edbf865c12f6..66541bcf497a5ebee44da6a8ca34a8e0e4e0b2d3 100644
--- a/ios/chrome/browser/ui/history/favicon_view_provider_unittest.mm
+++ b/ios/chrome/browser/ui/history/favicon_view_provider_unittest.mm
@@ -9,7 +9,6 @@
 #include "base/files/file_path.h"
 #include "base/files/file_util.h"
 #include "base/location.h"
-#include "base/mac/scoped_nsobject.h"
 #include "base/path_service.h"
 #include "base/single_thread_task_runner.h"
 #include "base/strings/sys_string_conversions.h"
@@ -30,6 +29,10 @@
 #include "third_party/skia/include/core/SkColor.h"
 #include "url/gurl.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 @interface FaviconViewProvider (Testing)
 @property(nonatomic, retain) UIImage* favicon;
 @property(nonatomic, copy) NSString* fallbackText;
@@ -131,14 +134,14 @@ class FaviconViewProviderTest : public PlatformTest {
 TEST_F(FaviconViewProviderTest, Favicon) {
   id mock_delegate =
       [OCMockObject mockForProtocol:@protocol(FaviconViewProviderDelegate)];
-  base::scoped_nsobject<FaviconViewProvider> viewProvider(
+  FaviconViewProvider* viewProvider =
       [[FaviconViewProvider alloc] initWithURL:GURL(kTestFaviconURL)
                                    faviconSize:kTestFaviconSize
                                 minFaviconSize:kTestFaviconSize
                               largeIconService:large_icon_service_.get()
-                                      delegate:mock_delegate]);
+                                      delegate:mock_delegate];
   void (^confirmationBlock)(NSInvocation*) = ^(NSInvocation* invocation) {
-    FaviconViewProvider* viewProvider;
+    __unsafe_unretained FaviconViewProvider* viewProvider;

[noyau (Ping after 24h), 2017/01/27 16:04:38]

Needs a comment.

[stkhapugin, 2017/02/02 15:29:23]

Don't think this needs a comment:
This is the only way one can use [NSInvocation getArgument:atIndex:] with ARC.
Expect to see a lot of this in unit tests. 

     [invocation getArgument:&viewProvider atIndex:2];
     EXPECT_NSNE(nil, viewProvider.favicon);
   };
@@ -152,16 +155,16 @@ TEST_F(FaviconViewProviderTest, Favicon) {
 TEST_F(FaviconViewProviderTest, FallbackIcon) {
   id mock_delegate =
       [OCMockObject mockForProtocol:@protocol(FaviconViewProviderDelegate)];
-  base::scoped_nsobject<FaviconViewProvider> item([[FaviconViewProvider alloc]
-           initWithURL:GURL(kTestFallbackURL)
-           faviconSize:kTestFaviconSize
-        minFaviconSize:kTestFaviconSize
-      largeIconService:large_icon_service_.get()
-              delegate:mock_delegate]);
+  FaviconViewProvider* item =
+      [[FaviconViewProvider alloc] initWithURL:GURL(kTestFallbackURL)
+                                   faviconSize:kTestFaviconSize
+                                minFaviconSize:kTestFaviconSize
+                              largeIconService:large_icon_service_.get()
+                                      delegate:mock_delegate];
 
   // Confirm that fallback text and color have been set before delegate call.
   void (^confirmationBlock)(NSInvocation*) = ^(NSInvocation* invocation) {
-    FaviconViewProvider* viewProvider;
+    __unsafe_unretained FaviconViewProvider* viewProvider;

[sczs, 2017/01/27 18:55:40]

There's probably a good reason, just want to know why use __unsafe_unretained
instead of __weak, if this is ARC __weak should be supported right?

[stkhapugin, 2017/02/02 15:29:23]

Unfortunately in this case only __unsafe_uretained can be used, because ARC
cannot infer any memory semantics when you do NSInvocation getArgument:atIndex:.
This is okay because when an invocation exists, you expect its arguments to be
properly memory managed, and you are usually not going to affect object
lifetimes anyway, just like here. 

     [invocation getArgument:&viewProvider atIndex:2];
     // Fallback text is the first letter of the URL.
     NSString* defaultText = @"T";