cc: Don't activate rasterize on demand when we have 0 memory.

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 6aadfb724cbf0ee44f9ffcde292998ac591a003e..16a0a55d03f4371ed2f9f7e43387efe224380f83 100644
--- a/cc/resources/tile_manager.cc
+++ b/cc/resources/tile_manager.cc
@@ -511,8 +511,12 @@ void TileManager::DidFinishRunningTasks(TaskSet task_set) {
     // We don't reserve memory for required-for-activation tiles during
     // accelerated gestures, so we just postpone activation when we don't
     // have these tiles, and activate after the accelerated gesture.
+    // Likewise if we don't have any memory (as is the case when we're
+    // invisible), if we have tiles that aren't ready, then we shouldn't

[reveman, 2014/09/23 02:38:54]

Why is 0 the magic number here? Seems wrong to assume that memory limit is 0
when invisible. What if it's 1 byte or the size of 5 tiles?

Would it be better to not allow rasterize-on-demand unless visible?

[vmpstr, 2014/09/23 15:29:22]

Good point. Do you think we should make it a part of global_state_ or pass it to
ManageTiles as a separate variable? I don't really think adding another client
function is appropriate here since we can just directly pass the value.

[reveman, 2014/09/23 16:39:11]

Maybe it's fine to just use "global_state_.memory_limit_policy != ALLOW_NOTHING"
here if we just update the description in tile_priority.h to make it more
explicit that this policy is always used when invisible. Wdyt?

[vmpstr, 2014/09/23 17:25:32]

Done.

+    // activate as activation can cause checkerboards.
     bool allow_rasterize_on_demand =
-        global_state_.tree_priority != SMOOTHNESS_TAKES_PRIORITY;
+        global_state_.tree_priority != SMOOTHNESS_TAKES_PRIORITY &&
+        global_state_.hard_memory_limit_in_bytes != 0;
 
     // Use on-demand raster for any required-for-activation tiles that have not
     // been been assigned memory after reaching a steady memory state. This