[cc] Evict UIResources when the renderer is not visible

cc/trees/thread_proxy.cc

Index: cc/trees/thread_proxy.cc
diff --git a/cc/trees/thread_proxy.cc b/cc/trees/thread_proxy.cc
index dda25ecb79ad4b24337fa6a00cda38c3bbd4b5e6..06298c0d27c66f719785f4b32bd5e3f0c4c5db0e 100644
--- a/cc/trees/thread_proxy.cc
+++ b/cc/trees/thread_proxy.cc
@@ -691,6 +691,8 @@ void ThreadProxy::ScheduledActionSendBeginFrameToMainThread() {
   }
   begin_frame_state->memory_allocation_limit_bytes =
       layer_tree_host_impl_->memory_allocation_limit_bytes();
+  begin_frame_state->evicted_ui_resources =
+      layer_tree_host_impl_->EvictedUIResourcesExist();
   Proxy::MainThreadTaskRunner()->PostTask(
       FROM_HERE,
       base::Bind(&ThreadProxy::BeginFrameOnMainThread,
@@ -765,6 +767,13 @@ void ThreadProxy::BeginFrameOnMainThread(
         UnlinkAndClearEvictedBackings();
   }
 
+  // Recreate all UI resources if there were evicted UI resources when the impl

[aelias_OOO_until_Jul13, 2013/09/10 20:02:33]

Hmm, I don't know of anything that guarantees no commit will ever occur when
invisible, so you're at risk of a random commit on an invisible tab defeating
your memory saving.  Do we need to tie recreation more explicitly to visibility?

[ccameron, 2013/09/10 21:27:49]

Only forced commits will happen, which I'm told is very rare when not visible
(like, for the thumbnailer). It looks like there are some issues with resource
eviction in that path already. In particular
- either all non-UI memory is evicted and the thumbnailer paints nothing
- the non-UI memory is recreated and we end up wasting GPU memory

Given the situation, I'd prefer to leave this as it is, and address "what
exactly do non-visible commits get" in another bug.
I prefer recreation coming in through commits rather than visibility, because it
is easier to reason about correctness through commits. Also, it matches
ContentsTexturesPurged, so there are fewer distinct systems.

It may be that we should re-dump all resources after forced commits when
backgrounded -- but this needs to be fixed for UI and non-UI resources.

+  // thread initiated the commit.
+  bool evicted_ui_resources =
+      begin_frame_state ? begin_frame_state->evicted_ui_resources : false;
+  if (evicted_ui_resources)
+      layer_tree_host_->RecreateUIResources();
+
   layer_tree_host_->Layout();
 
   // Clear the commit flag after updating animations and layout here --- objects
@@ -773,7 +782,9 @@ void ThreadProxy::BeginFrameOnMainThread(
   commit_requested_ = false;
   commit_request_sent_to_impl_thread_ = false;
   bool can_cancel_this_commit =
-      can_cancel_commit_ && !in_composite_and_readback_;
+      can_cancel_commit_ &&
+      !in_composite_and_readback_ &&
+      !evicted_ui_resources;
   can_cancel_commit_ = true;
 
   scoped_ptr<ResourceUpdateQueue> queue =
@@ -1353,7 +1364,7 @@ size_t ThreadProxy::MaxPartialTextureUpdates() const {
 }
 
 ThreadProxy::BeginFrameAndCommitState::BeginFrameAndCommitState()
-    : memory_allocation_limit_bytes(0) {}
+    : memory_allocation_limit_bytes(0), evicted_ui_resources(false) {}
 
 ThreadProxy::BeginFrameAndCommitState::~BeginFrameAndCommitState() {}
 
@@ -1458,6 +1469,7 @@ void ThreadProxy::RenewTreePriority() {
   // evicted resources or there is an invalid viewport size.
   if (layer_tree_host_impl_->active_tree()->ContentsTexturesPurged() ||
       layer_tree_host_impl_->active_tree()->ViewportSizeInvalid() ||
+      layer_tree_host_impl_->EvictedUIResourcesExist() ||
       input_throttled_until_commit_)
     priority = NEW_CONTENT_TAKES_PRIORITY;