[M120 Migration][Canvas2D] Do not disable acceleration on gpu readback.

[M120 Migration][Canvas2D] Do not disable acceleration on gpu readback.

On M76 and earlier acceleration is disabled on readbacks based on
heuristics, but currently for gpu readback canvas2d acceleration is
disabled straightaway and heuristics are removed in upstream[1,2]. This
impacts performance of canvasmark KPI heavily. Hence we dont disable
acceleration during gpu readbacks.

Performance(TV):
Ubrowser CanvasMark
Before: 28.8, 29.0, 29.2, 29.0, 29.1
After: 33.3, 32.4, 32.5, 33.3, 33.5

References:
[1] https://chromium-review.googlesource.com/c/chromium/src/+/1845511
[2] https://chromium-review.googlesource.com/c/chromium/src/+/1752546
[3] https://review.tizen.org/gerrit/291138

Change-Id: I5c8388a042e0bbe17bca5a635aeace8959587640
Signed-off-by: Satyaveer Singh <satyaveer.s@samsung.com>