cc: Separate raster and decode prepaint regions.

cc/trees/layer_tree_settings.cc

Index: cc/trees/layer_tree_settings.cc
diff --git a/cc/trees/layer_tree_settings.cc b/cc/trees/layer_tree_settings.cc
index d13a01606ba04d5f7bf4450376a0b5f7a04260af..a21b755ece8d087f9719f1c92f96924c66e58fa5 100644
--- a/cc/trees/layer_tree_settings.cc
+++ b/cc/trees/layer_tree_settings.cc
@@ -110,6 +110,7 @@ LayerTreeSettings::LayerTreeSettings()
                      ManagedMemoryPolicy::kDefaultNumResourcesLimit),
       gpu_decoded_image_budget_bytes(96 * 1024 * 1024),
       software_decoded_image_budget_bytes(128 * 1024 * 1024),
+      max_preraster_distance_in_screen_pixels(1000),

[ericrk, 2016/05/24 23:42:34]

I'm curious if we should use an even lower limit for GPU? With the skewport
target time set to 0.2s for GPU, you'd have to scroll at a rate of 5000 pixels
per second to hit this - additionally, GPU should be able to raster more quickly
than SW, especially if no image decodes are necessary.

[vmpstr, 2016/06/07 20:43:55]

That's entirely possible. Eventually I'd like this to be close to 0, however I'm
trying to deliberately be a bit conservative so that we don't break things if
our assumptions about imageless raster speed are wrong. Do you think this is a
good value to start with?

       use_cached_picture_raster(true) {}
 
 LayerTreeSettings::LayerTreeSettings(const LayerTreeSettings& other) = default;