Modifies BlockCleanupTest so that it can be used from ARC code.

ios/chrome/test/block_cleanup_test.mm

Index: ios/chrome/test/block_cleanup_test.mm
diff --git a/ios/chrome/test/block_cleanup_test.mm b/ios/chrome/test/block_cleanup_test.mm
index 06ac9e4c93c4b1aa91b096a1f2a90dcc3e365cb1..5b350578d02c3a0469c9defd4e6aba4a3f42acb6 100644
--- a/ios/chrome/test/block_cleanup_test.mm
+++ b/ios/chrome/test/block_cleanup_test.mm
@@ -8,6 +8,7 @@
 
 #include "base/logging.h"
 #import "base/mac/scoped_nsobject.h"
+#import "base/mac/foundation_util.h"
 
 void BlockCleanupTest::SetUp() {
   block_cleanup_pool_ = [[NSAutoreleasePool alloc] init];
@@ -22,7 +23,7 @@ void BlockCleanupTest::TearDown() {
   // Drain the autorelease pool to finish cleaning up after blocks.
   // TODO(rohitrao): Can this be an EXPECT, so as to not crash the whole suite?
   DCHECK(block_cleanup_pool_);
-  [block_cleanup_pool_ release];
+  [base::mac::ObjCCastStrict<NSAutoreleasePool>(block_cleanup_pool_) release];
   block_cleanup_pool_ = nil;
 
   PlatformTest::TearDown();