Track UMA stats for running out of tile 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 d508f6a0a17a5639290949fb9cf083eb4ffb6e10..1a368c0103a2d2908d706f2ceae98b29948b067c 100644
--- a/cc/resources/tile_manager.cc
+++ b/cc/resources/tile_manager.cc
@@ -874,6 +874,8 @@ void TileManager::AssignGpuMemoryToTiles(
                       global_state_.hard_memory_limit_in_bytes,
                       "over",
                       bytes_that_exceeded_memory_budget);
+
+    UMA_HISTOGRAM_BOOLEAN("TileManager.ExceededMemoryBudget", true);

[vmpstr, 2014/07/05 17:34:41]

I think what we should have is

UMA_HISTOGRAM_BOOLEAN(..., oomed_hard);

The problem with the current approach is that we will never see a "false" in
this boolean, so the usefulness of seeing "true" a bunch of times is
questionable. Furthermore, if you report it in "ever exceeded" block, then once
we exceed the memory then for the lifetime of tile manager, we will always
report true (even if it goes back under the memory limit). 

   }
   memory_stats_from_last_assign_.total_budget_in_bytes =
       global_state_.hard_memory_limit_in_bytes;