memory coordinator: Throttle background renderers on Android

content/browser/memory/memory_coordinator.cc

Index: content/browser/memory/memory_coordinator.cc
diff --git a/content/browser/memory/memory_coordinator.cc b/content/browser/memory/memory_coordinator.cc
index 5bf29c78e1d6afbb11fe113de6507c3193f24188..a0e509b62b1c9eb58f9c99cb2bdfcf6f91ee34f5 100644
--- a/content/browser/memory/memory_coordinator.cc
+++ b/content/browser/memory/memory_coordinator.cc
@@ -88,10 +88,7 @@ bool MemoryCoordinator::SetChildMemoryState(int render_process_id,
   if (!iter->second.handle->child().is_bound())
     return false;
 
-  // We don't suspend foreground renderers. Throttle them instead.
-  if (memory_state == mojom::MemoryState::SUSPENDED &&
-      iter->second.is_visible)
-    memory_state = mojom::MemoryState::THROTTLED;
+  memory_state = OverrideChildState(memory_state, iter->second);

[haraken, 2016/12/09 03:48:50]

OverrideGlobalState ?

I might want to unify terms into "global states" and "local states".

[bashi, 2016/12/09 04:18:45]

Done. Maybe "Override" isn't a good verb for this method. There will be better
name for this method but I couldn't come up with better names.
We can replace "the current state" with "local state" but we still need to say
"child states".

 
   // A nop doesn't need to be sent, but is considered successful.
   if (iter->second.memory_state == memory_state)
@@ -173,6 +170,23 @@ bool MemoryCoordinator::CanSuspendRenderer(int render_process_id) {
   return delegate_->CanSuspendBackgroundedRenderer(render_process_id);
 }
 
+mojom::MemoryState MemoryCoordinator::OverrideChildState(
+    mojom::MemoryState memory_state,
+    const ChildInfo& child) {
+  // We don't suspend foreground renderers. Throttle them instead.
+  if (child.is_visible && memory_state == mojom::MemoryState::SUSPENDED)
+    return mojom::MemoryState::THROTTLED;
+#if defined(OS_ANDROID)
+  // On Android, we throttle background renderers immediately.
+  // TODO(bashi): Create a specialized class of MemoryCoordinator for Android
+  // and move this ifdef to the class.
+  if (!child.is_visible && memory_state == mojom::MemoryState::NORMAL)
+    return mojom::MemoryState::THROTTLED;
+  // TODO(bashi): Suspend background renderers after a certain period of time.
+#endif  // defined(OS_ANDROID)
+  return memory_state;
+}
+
 void MemoryCoordinator::SetDelegateForTesting(
     std::unique_ptr<MemoryCoordinatorDelegate> delegate) {
   CHECK(!delegate_);