CC/GPU: Add a soft limit to the compositor.

cc/trees/layer_tree_host_impl.cc

 // Copyright 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/trees/layer_tree_host_impl.h"
 
 #include <algorithm>
 #include <limits>
 
 #include "base/basictypes.h"
@@ skipping 1153 matching lines @@
   UpdateTileManagerMemoryPolicy(policy);
 }
 
 void LayerTreeHostImpl::UpdateTileManagerMemoryPolicy(
     const ManagedMemoryPolicy& policy) {
   if (!tile_manager_)
     return;
 
   // TODO(reveman): We should avoid keeping around unused resources if
   // possible. crbug.com/224475
-  global_tile_state_.memory_limit_in_bytes =
-      visible_ ?
-      policy.bytes_limit_when_visible : 0;
+  global_tile_state_.hard_memory_limit_in_bytes = 0;
+  global_tile_state_.soft_memory_limit_in_bytes = 0;
+  if (visible_ && policy.bytes_limit_when_visible > 0) {
+    global_tile_state_.hard_memory_limit_in_bytes =
+        policy.bytes_limit_when_visible;
+    global_tile_state_.soft_memory_limit_in_bytes =
+        global_tile_state_.hard_memory_limit_in_bytes *
+        settings_.max_memory_for_prepaint_percentage / 100;
+  }
+  // Unused limit is calculated from soft-limit, as hard-limit may
+  // be very high and shouldn't typically be exceeded.
   global_tile_state_.unused_memory_limit_in_bytes = static_cast<size_t>(
-      (static_cast<int64>(global_tile_state_.memory_limit_in_bytes) *
-       settings_.max_unused_resource_memory_percentage) / 100);
+      (static_cast<int64>(global_tile_state_.soft_memory_limit_in_bytes) *
+       settings_.max_unused_resource_memory_percentage) /
+      100);
   global_tile_state_.memory_limit_policy =
       ManagedMemoryPolicy::PriorityCutoffToTileMemoryLimitPolicy(
           visible_ ?
           policy.priority_cutoff_when_visible :
           gpu::MemoryAllocation::CUTOFF_ALLOW_NOTHING);
   global_tile_state_.num_resources_limit = policy.num_resources_limit;
 
   DidModifyTilePriorities();
 }
 
@@ skipping 1802 matching lines @@
   swap_promise_monitor_.erase(monitor);
 }
 
 void LayerTreeHostImpl::NotifySwapPromiseMonitorsOfSetNeedsRedraw() {
   std::set<SwapPromiseMonitor*>::iterator it = swap_promise_monitor_.begin();
   for (; it != swap_promise_monitor_.end(); it++)
     (*it)->OnSetNeedsRedrawOnImpl();
 }
 
 }  // namespace cc