Set IdleHandler timer on background threads a minimum of 30s in the future after initial run.

content/renderer/render_thread_impl.cc

Index: content/renderer/render_thread_impl.cc
diff --git a/content/renderer/render_thread_impl.cc b/content/renderer/render_thread_impl.cc
index 7500b23750482e9fa0c802d754826ca0c8857db3..d0715765e2629d6fe4d999f022b278df7a9f3adf 100644
--- a/content/renderer/render_thread_impl.cc
+++ b/content/renderer/render_thread_impl.cc
@@ -1052,7 +1052,7 @@ void RenderThreadImpl::IdleHandler() {
   // Dampen the delay using the algorithm (if delay is in seconds):
   //    delay = delay + 1 / (delay + 2)
   // Using floor(delay) has a dampening effect such as:
-  //    30s, 30, 30, 31, 31, 31, 31, 32, 32, ...
+  //    30s repeated > 30 times, 31s repeated > 30 times, 32s...
   // If the delay is in milliseconds, the above formula is equivalent to:
   //    delay_ms / 1000 = delay_ms / 1000 + 1 / (delay_ms / 1000 + 2)
   // which is equivalent to