Fixed leak on LRU snapshot cache implementation.

ios/chrome/browser/snapshots/snapshot_cache.mm

Index: ios/chrome/browser/snapshots/snapshot_cache.mm
diff --git a/ios/chrome/browser/snapshots/snapshot_cache.mm b/ios/chrome/browser/snapshots/snapshot_cache.mm
index b76ba6ec4889a46a04b4918c50947aa44e51b81c..d8151e2f790167b2bd466186ec27f7fe05f38c59 100644
--- a/ios/chrome/browser/snapshots/snapshot_cache.mm
+++ b/ios/chrome/browser/snapshots/snapshot_cache.mm
@@ -390,7 +390,7 @@ void ConvertAndSaveGreyImage(
   DCHECK(!IsIPadIdiom());
   DCHECK_CURRENTLY_ON_WEB_THREAD(web::WebThread::UI);
   NSMutableDictionary* dictionary =

[sdefresne, 2016/02/09 16:17:07]

nit: the recommended pattern in Chromium is to use base::scoped_nsobject<>
instead of autorelease/retain.

[jbbegue (google), 2016/02/10 15:10:22]

Done.

-      [[NSMutableDictionary alloc] initWithCapacity:2];
+      [[[NSMutableDictionary alloc] initWithCapacity:2] autorelease];
   for (NSString* sessionID in pinnedIDs_) {
     UIImage* image = nil;
     if (lruCache_)
@@ -405,7 +405,7 @@ void ConvertAndSaveGreyImage(
     for (NSString* sessionID in pinnedIDs_)
       [lruCache_ setObject:dictionary[sessionID] forKey:sessionID];
   } else {
-    imageDictionary_.reset(dictionary);
+    imageDictionary_.reset([dictionary retain]);
   }
 }