When `{meme ...}` embed has no text, just use the raw file data unmodified
Summary:
Ref T13216. See PHI948. When you use the remarkup hint button to embed a meme with no text, you get `{meme src=X}`.
If the source is a GIF, we currently split the source apart into frame-by-frame images, process them, and stitch them back together. The end result is the same image we started with, but this process can be slow/expensive, and may timeout for sufficiently large GIFs.
Instead: when there's no text, just return the original image data.
Test Plan:
- Used `{meme src=X}` with no text, got an image faster.
- Used `{meme src=X, above=...}` to add text, got an attempt to add text (which didn't get very far locally since I don't have GD configured).
Reviewers: amckinley
Reviewed By: amckinley
Maniphest Tasks: T13216
Differential Revision: https://secure.phabricator.com/D19777