Add failure methods to thumbnail service.

SignalServiceKit/src/Messages/Attachments/OWSThumbnailService.swift

@@ -86,7 +86,7 @@ private struct OWSThumbnailRequest {
 
     // completion will only be called on success.
     // completion will be called async on the main thread.
-    @objc public func ensureThumbnailForAttachmentId(attachmentId: String,
+    @objc public func ensureThumbnail(forAttachmentId attachmentId: String,
                                                      thumbnailDimensionPoints: UInt,
                                                      success: @escaping SuccessBlock,
                                                      failure: @escaping FailureBlock) {

SignalServiceKit/src/Messages/Attachments/TSAttachmentStream.m

@@ -726,10 +726,10 @@ typedef void (^OWSLoadedThumbnailSuccess)(OWSLoadedThumbnail *loadedThumbnail);
         return [[OWSLoadedThumbnail alloc] initWithImage:image filePath:thumbnailPath];
     }
 
-    [OWSThumbnailService.shared ensureThumbnailForAttachmentIdWithAttachmentId:self.uniqueId
-                                                      thumbnailDimensionPoints:thumbnailDimensionPoints
-                                                                       success:success
-                                                                       failure:failure];
+    [OWSThumbnailService.shared ensureThumbnailForAttachmentId:self.uniqueId
+                                      thumbnailDimensionPoints:thumbnailDimensionPoints
+                                                       success:success
+                                                       failure:failure];
     return nil;
 }