Don't hold onto SkBitmap in mus_demo.

There is no need to hold onto the SkBitmap object as a member variable
in MusDemo. It was originally retained so that the pixel buffer didn't
need to be reallocated for each frame (a copy of the pixel buffer was
made when submitting the frame). However, the pixel buffer is now locked
and ownership is shared with the gfx::ImageSkiaRep, requiring a new
pixel buffer to be allocated for each frame regardless. Remove |bitmap_|
member variable.

BUG=none

Review-Url: https://codereview.chromium.org/2581163003
Cr-Commit-Position: refs/heads/master@{#439129}
2 files changed