cc: Make tiles that are not required by trees NEVER_BIN

cc/resources/tile_manager.cc

Index: cc/resources/tile_manager.cc
diff --git a/cc/resources/tile_manager.cc b/cc/resources/tile_manager.cc
index 48cb31fe608f9c1efaf8c0f4799b393c6a330678..6f79f731282f2498245b6a062a1846f7cdae51c6 100644
--- a/cc/resources/tile_manager.cc
+++ b/cc/resources/tile_manager.cc
@@ -27,6 +27,9 @@ namespace {
 // things we need soon, and eventually.
 inline TileManagerBin BinFromTilePriority(const TilePriority& prio,
                                           TreePriority tree_priority) {
+  if (!prio.required_by_tree)

[reveman, 2013/06/21 01:59:16]

is there a case where this is different than "distance_to_visible_in_pixels ==
std::numeric_limits<float>::infinity()"? I'd prefer to use that if possible but
I'm OK with this too.

nit: move this check below the constants. I don't see a reason for this to be
different than the other if statements.

+    return NEVER_BIN;
+
   // The amount of time for which we want to have prepainting coverage.
   const float kPrepaintingWindowTimeSeconds = 1.0f;
   const float kBackflingGuardDistancePixels = 314.0f;