Allow one-copy task tile worker pool to use compressed textures.

cc/output/renderer_settings.h

Index: cc/output/renderer_settings.h
diff --git a/cc/output/renderer_settings.h b/cc/output/renderer_settings.h
index 48aa13d00541f4fdb93102a94d71d37108e119ed..44d67e7cf1030f03f9e659f0d811e76cc53110e9 100644
--- a/cc/output/renderer_settings.h
+++ b/cc/output/renderer_settings.h
@@ -27,6 +27,7 @@ class CC_EXPORT RendererSettings {
   int highp_threshold_min;
   bool use_rgba_4444_textures;
   size_t texture_id_allocation_chunk_size;
+  bool use_tile_compression;

[reveman, 2015/09/30 09:55:15]

Can we merge this with use_rgba_4444_textures somehow? E.g. replace both with a
tile_resource_format setting. Maybe
tile_resource_format+tile_resource_format_with_alpha so the embedder can also
chose the format used when alpha is required.

[christiank, 2015/11/26 15:35:35]

This would be good, I agree. I think we'd need a new enum for this since we need
an option for (!use_rgba_444_textures && !use_tile_compression). I don't think
using ResourceFormat for this would work as it has no default format. Replacing
ResourceProvider::best_texture_format() with a setting looks tricky. Perhaps
something like this would work?

enum class MemoryEfficientResourceFormat {
  NONE,
  RGBA_4444,
  ETC1,
};

MemoryEfficientResourceFormat memory_efficient_format;
MemoryEfficientResourceFormat memory_efficient_format_with_alpha;

What do you think?

[reveman, 2015/11/27 16:46:49]

Can we just use ResourceFormat and require it to be set to RGBA_8888 or
equivalent when compressed formats shouldn't be used? 

[christiank, 2015/11/30 15:41:08]

Yes, that would work. I have made this change now, not sure if I should document
this behavior somewhere?

 };
 
 }  // namespace cc