cc: Change max_tiles_for_interest_rect to be screen pixels padding.

cc/layers/picture_layer_impl_unittest.cc

Index: cc/layers/picture_layer_impl_unittest.cc
diff --git a/cc/layers/picture_layer_impl_unittest.cc b/cc/layers/picture_layer_impl_unittest.cc
index ce0956e610481adbf726d2a39644b84797d92773..73447dfd04e118be51534bf0131b3b2db72c66b1 100644
--- a/cc/layers/picture_layer_impl_unittest.cc
+++ b/cc/layers/picture_layer_impl_unittest.cc
@@ -4752,7 +4752,7 @@ TEST_F(PictureLayerImplTest, ScrollPastLiveTilesRectAndBack) {
       gfx::Transform(),              // transform
       gfx::Rect(),                   // clip
       gfx::Rect(),                   // viewport
-      gfx::Rect(0, 1000, 100, 100),  // viewport_rect_for_tile_priority
+      gfx::Rect(0, 5000, 100, 100),  // viewport_rect_for_tile_priority

[weiliangc, 2015/07/15 19:56:09]

Not sure why are we changing to 5k?

[vmpstr, 2015/07/16 00:31:03]

So we set the tile size to be 100, 100 and so in order to ensure that the layer
is offscreen it was enough to set the viewport to be at 0, 1000. However, by
using 3k as the padding, this is no longer sufficient. So this just moves it
"far enough away" to not be in the interest rect, which is the intent of this
test.

       gfx::Transform(),              // transform_for_tile_priority
       false);