D3D11: Don't use staging buffer for dynamic streaming buffers

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Currently, we buffers with usage "DYNAMIC_DRAW" use a staging buffer in D3D11 
to store dynamic data. Iur current design has a weakness of copying way too 
much data from the staging texture unnecessarily: for small updates, we can 
copy the entire staging texture.

At one point we had a design which uses a CPU-side cache (see 
https://chromium-review.googlesource.com/213813). We reverted this for a 
simpler, more robust fix, but we can fix the performance by using a similar CPU 
dynamic data cache instead of a D3D11 staging buffer.

Original issue reported on code.google.com by jmad...@chromium.org on 11 Feb 2015 at 9:26

[GoogleCodeExporter]

Note: I should also make a performance test for this.

Original comment by jmad...@chromium.org on 11 Feb 2015 at 9:27

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[GoogleCodeExporter]

Fixed in https://chromium-review.googlesource.com/#/c/249183/.

Existing perf tests cover the regression.

Original comment by jmad...@chromium.org on 24 Feb 2015 at 10:03

• Changed state: Fixed
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