Respond to CR.

Signal/src/ViewControllers/ConversationView/Cells/OWSGenericAttachmentView.m

@@ -159,6 +159,9 @@ NS_ASSUME_NONNULL_BEGIN
                        .fileSize;
         OWSAssertDebug(!error);
     }
+    // We don't want to show the file size while the attachment is downloading.
+    // To avoid layout jitter when the download completes, we reserve space in
+    // the layout using a whitespace string.
     NSString *bottomText = @" ";
     if (fileSize > 0) {
         bottomText = [OWSFormat formatFileSize:fileSize];

Signal/src/ViewControllers/ConversationView/ConversationViewItem.m

@@ -990,6 +990,7 @@ NSString *NSStringForOWSMessageCellType(OWSMessageCellType cellType)
 - (BOOL)canCopyMedia
 {
     if (self.attachmentPointer != nil) {
+        // The attachment is still downloading.
         return NO;
     }
 
@@ -1018,6 +1019,7 @@ NSString *NSStringForOWSMessageCellType(OWSMessageCellType cellType)
 - (BOOL)canSaveMedia
 {
     if (self.attachmentPointer != nil) {
+        // The attachment is still downloading.
         return NO;
     }
 
@@ -1143,6 +1145,7 @@ NSString *NSStringForOWSMessageCellType(OWSMessageCellType cellType)
 - (BOOL)hasMediaActionContent
 {
     if (self.attachmentPointer != nil) {
+        // The attachment is still downloading.
         return NO;
     }
 

SignalServiceKit/src/Messages/Attachments/TSAttachmentPointer.m

@@ -14,7 +14,7 @@ NS_ASSUME_NONNULL_BEGIN
 
 @interface TSAttachmentStream (TSAttachmentPointer)
 
-- (CGSize)cachedImageSize;
+- (CGSize)cachedMediaSize;
 
 @end
 
@@ -100,7 +100,7 @@ NS_ASSUME_NONNULL_BEGIN
     _state = TSAttachmentPointerStateEnqueued;
     self.attachmentType = attachmentStream.attachmentType;
     _pointerType = TSAttachmentPointerTypeRestoring;
-    _mediaSize = (attachmentStream.shouldHaveImageSize ? attachmentStream.cachedImageSize : CGSizeZero);
+    _mediaSize = (attachmentStream.shouldHaveImageSize ? attachmentStream.cachedMediaSize : CGSizeZero);
 
     return self;
 }
@@ -119,7 +119,9 @@ NS_ASSUME_NONNULL_BEGIN
     NSString *_Nullable fileName = attachmentProto.fileName;
     NSString *_Nullable contentType = attachmentProto.contentType;
     if (contentType.length < 1) {
-        OWSLogError(@"Invalid attachment content type.");
+        // Content type might not set if the sending client can't
+        // infer a MIME type from the file extension.
+        OWSLogWarn(@"Invalid attachment content type.");
         NSString *_Nullable fileExtension = [fileName pathExtension].lowercaseString;
         if (fileExtension.length > 0) {
             contentType = [MIMETypeUtil mimeTypeForFileExtension:fileExtension];

SignalServiceKit/src/Messages/Attachments/TSAttachmentStream.m

@@ -526,7 +526,7 @@ typedef void (^OWSLoadedThumbnailSuccess)(OWSLoadedThumbnail *loadedThumbnail);
     }
 }
 
-- (CGSize)cachedImageSize
+- (CGSize)cachedMediaSize
 {
     OWSAssertDebug(self.shouldHaveImageSize);