data_decoder: Use inline bitmap data for animations

Using a normal skia Bitmap mojom type means that large frames may be
transmitted as shared memory regions, which in turn means that
animations with more than 64 large frames can cause DecodeAnimation's
reply to exceed Mojo's self-imposed per-message handle limitation.

This is a temporary solution which restores DecodeAnimation to using
inline bitmap data (which it did prior to CL:1004598).

Bug: 838706
Change-Id: I53542a0070b6d554b52c6b0e3576b94af233a9f4
Reviewed-on: https://chromium-review.googlesource.com/1038760Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Commit-Queue: Ken Rockot <rockot@chromium.org>
Cr-Commit-Position: refs/heads/master@{#555293}

services/data_decoder/public/mojom/image_decoder.mojom

@@ -15,7 +15,9 @@ enum ImageCodec {
 };
 
 struct AnimationFrame {
-  skia.mojom.Bitmap bitmap;
+  // TODO(https://crbug.com/838706): Cnonsider replacing individual Bitmap
+  // structs with a new type that uses a single BigBuffer for all frame data.
+  skia.mojom.InlineBitmap bitmap;
   mojo_base.mojom.TimeDelta duration;
 };