cc: Add a tile manager check to try and diagnose renderer hangs.

cc/tiles/tile_manager.cc

Index: cc/tiles/tile_manager.cc
diff --git a/cc/tiles/tile_manager.cc b/cc/tiles/tile_manager.cc
index 08796a32f949f1064dec57a5b0a9883a89e990ab..5a9d737e491e057ada0830fc93f0eb39110e5ed4 100644
--- a/cc/tiles/tile_manager.cc
+++ b/cc/tiles/tile_manager.cc
@@ -1071,7 +1071,10 @@ bool TileManager::AreRequiredTilesReadyToDraw(
   // have to iterate the queue to check whether the required tiles are ready to
   // draw.
   for (; !raster_priority_queue->IsEmpty(); raster_priority_queue->Pop()) {
-    if (!raster_priority_queue->Top().tile()->draw_info().IsReadyToDraw())
+    const auto& prioritized_tile = raster_priority_queue->Top();
+    // TODO(vmpstr): Check to debug crbug.com/622080. Remove when fixed.

[sunnyps, 2016/12/10 01:29:47]

Shouldn't we do this check only for the required for activation queue?

+    CHECK_EQ(prioritized_tile.priority().priority_bin, TilePriority::NOW);
+    if (!prioritized_tile.tile()->draw_info().IsReadyToDraw())
       return false;
   }