Revert of cc: Call PrepareTiles when becoming visible in browser only.

cc/trees/layer_tree_host_impl.cc

Index: cc/trees/layer_tree_host_impl.cc
diff --git a/cc/trees/layer_tree_host_impl.cc b/cc/trees/layer_tree_host_impl.cc
index 84740087d8d2cdf59b20190e768628f070a9f3e6..ee9afe43ec75dd81cd7d6b416e1add1182c2fdf9 100644
--- a/cc/trees/layer_tree_host_impl.cc
+++ b/cc/trees/layer_tree_host_impl.cc
@@ -1988,9 +1988,11 @@
   else
     EvictAllUIResources();
 
-  // PrepareTiles when becoming invisible so that we evict tiles immediately.
-  if (!visible_)
-    PrepareTiles();
+  // Call PrepareTiles unconditionally on visibility change since this tab may
+  // never get another draw or timer tick. When becoming visible we care about
+  // unblocking the scheduler which might be waiting for activation / ready to
+  // draw. When becoming invisible we care about evicting tiles immediately.
+  PrepareTiles();
 
   if (!renderer_)
     return;