Revert of Temporarily disable context idle cleanup.

cc/output/context_cache_controller.cc

Index: cc/output/context_cache_controller.cc
diff --git a/cc/output/context_cache_controller.cc b/cc/output/context_cache_controller.cc
index aec923235979c648ed03f208be34b2e212d25681..79e85b3e0336146e41e82aaaf4d0463e21d2e141 100644
--- a/cc/output/context_cache_controller.cc
+++ b/cc/output/context_cache_controller.cc
@@ -139,12 +139,6 @@
 }
 
 void ContextCacheController::OnIdle(uint32_t idle_generation) {
-// TODO(ericrk): Temporarily disabling this to investigate whether this
-// code regressed scroll latency on Android. crbug.com/664181
-#if defined(OS_ANDROID)
-  return;
-#endif
-
   // First check if we should run our idle callback at all. If we have become
   // busy since scheduling, just schedule another idle callback and return.
   {