ios: Stop using __weak.

ios/web/crw_browsing_data_store_unittest.mm

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #import "ios/web/public/crw_browsing_data_store.h"
 
 #include "base/ios/ios_util.h"
 #include "base/logging.h"
 #import "base/mac/scoped_nsobject.h"
 #include "base/memory/scoped_ptr.h"
@@ skipping 14 matching lines @@
 @property(nonatomic, assign) NSUInteger modeChangeCount;
 
 // |browsingDataStore| cannot be null.
 - (instancetype)initWithBrowsingDataStore:
     (CRWBrowsingDataStore*)browsingDataStore NS_DESIGNATED_INITIALIZER;
 - (instancetype)init NS_UNAVAILABLE;
 @end
 
 @implementation CRWTestBrowsingDataStoreObserver {
   // The underlying CRWBrowsingDataStore.
-  __weak CRWBrowsingDataStore* _browsingDataStore;
+  CRWBrowsingDataStore* _browsingDataStore;  // weak
 }
 
 @synthesize modeChangeCount = _modeChangeCount;
 
 - (instancetype)initWithBrowsingDataStore:
     (CRWBrowsingDataStore*)browsingDataStore {
   self = [super init];
   if (self) {
     DCHECK(browsingDataStore);
     [browsingDataStore addObserver:self
@@ skipping 194 matching lines @@
 
   ASSERT_EQ(ACTIVE, [browsing_data_store_ mode]);
 
   [browsing_data_store_ makeInactiveWithCompletionHandler:nil];
   // |removeDataOfTypes| is called immediately after a |makeInactive| call.
   RemoveDataOfTypes(BROWSING_DATA_TYPE_COOKIES);
   EXPECT_EQ(INACTIVE, [browsing_data_store_ mode]);
 }
 
 }  // namespace web