[ios] TabCollectionTabCell to use SnapshotCache.

ios/clean/chrome/browser/ui/tab_collection/tab_collection_tab_cell.mm

Index: ios/clean/chrome/browser/ui/tab_collection/tab_collection_tab_cell.mm
diff --git a/ios/clean/chrome/browser/ui/tab_collection/tab_collection_tab_cell.mm b/ios/clean/chrome/browser/ui/tab_collection/tab_collection_tab_cell.mm
index f9c79142e81d794817e10c73e155d2f0eb32c368..e6924b50868b41e729fd6c47f1189d720939fcb5 100644
--- a/ios/clean/chrome/browser/ui/tab_collection/tab_collection_tab_cell.mm
+++ b/ios/clean/chrome/browser/ui/tab_collection/tab_collection_tab_cell.mm
@@ -4,6 +4,7 @@
 
 #import "ios/clean/chrome/browser/ui/tab_collection/tab_collection_tab_cell.h"
 
+#import "ios/chrome/browser/snapshots/snapshot_cache.h"
 #import "ios/chrome/browser/ui/tab_switcher/tab_switcher_button.h"
 #import "ios/chrome/browser/ui/uikit_ui_util.h"
 #include "ios/chrome/grit/ios_theme_resources.h"
@@ -20,6 +21,8 @@ const CGFloat kSelectedBorderWidth = 4.0f;
 }
 
 @interface TabCollectionTabCell ()
+@property(nonatomic, strong) TabCollectionItem* item;
+@property(nonatomic, strong) SnapshotCache* snapshotCache;
 @property(nonatomic, strong) UILabel* titleLabel;
 @property(nonatomic, strong) UIImageView* favicon;
 @property(nonatomic, strong) TabSwitcherButton* snapshotButton;
@@ -27,6 +30,7 @@ const CGFloat kSelectedBorderWidth = 4.0f;
 
 @implementation TabCollectionTabCell
 @synthesize item = _item;
+@synthesize snapshotCache = _snapshotCache;
 @dynamic titleLabel;
 @dynamic favicon;
 @dynamic snapshotButton;
@@ -38,19 +42,41 @@ const CGFloat kSelectedBorderWidth = 4.0f;
   return self;
 }
 
-#pragma mark - Properties
+#pragma mark - Cell lifecycle
 
-- (void)setItem:(TabCollectionItem*)item {
+- (void)prepareForReuse {
+  [super prepareForReuse];
+  self.item = nil;
+  self.snapshotCache = nil;
+}
+
+#pragma mark - Public methods
+
+- (void)configureCell:(TabCollectionItem*)item
+        snapshotCache:(SnapshotCache*)snapshotCache {
   DCHECK(item);
-  _item = item;
+  self.item = item;
+  self.snapshotCache = snapshotCache;
   self.titleLabel.text = item.title;
   self.snapshotButton.accessibilityIdentifier =
       [NSString stringWithFormat:@"%@_button", item.title];
   self.contentView.accessibilityLabel = item.title;
   self.favicon.image = NativeImage(IDR_IOS_OMNIBOX_HTTP);
+  __weak TabCollectionTabCell* weakSelf = self;
+  [self.snapshotCache
+      retrieveImageForSessionID:self.item.tabID
+                       callback:^(UIImage* snapshot) {
+                         DCHECK([NSThread isMainThread]);

[marq (ping after 24h), 2017/07/06 12:41:17]

This check shouldn't be needed; if the contract is that the snapshot cache calls
back on the same thread, then the cache should be doing the DCHECK.

[edchin, 2017/07/06 14:47:18]

Done.

+                         // PLACEHOLDER: This operation will be cancellable.
+                         if ([weakSelf.item.tabID isEqualToString:item.tabID]) {
+                           [weakSelf.snapshotButton
+                               setImage:snapshot
+                               forState:UIControlStateNormal];
+                         }
+                       }];
 }
 
-#pragma mark - Private
+#pragma mark - Private methods
 
 - (void)setupSelectedBackgroundView {
   self.selectedBackgroundView = [[UIView alloc] init];