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

cc/resources/tile_manager.h

Index: cc/resources/tile_manager.h
diff --git a/cc/resources/tile_manager.h b/cc/resources/tile_manager.h
index 0e7de2cd5858e3914399e09fcc275422f0b7dfda..fc613781393f528abd58dccdf80ada2adaf3a921 100644
--- a/cc/resources/tile_manager.h
+++ b/cc/resources/tile_manager.h
@@ -105,11 +105,13 @@ class CC_EXPORT TileManager : public RasterWorkerPoolClient,
 
   void SetGlobalStateForTesting(
       const GlobalStateThatImpactsTilePriority& state) {
+    // Soft limit is used for resource pool such that
+    // memory returns to normal after going over.
     if (state != global_state_) {
       global_state_ = state;
       prioritized_tiles_dirty_ = true;
       resource_pool_->SetResourceUsageLimits(
-          global_state_.memory_limit_in_bytes,
+          global_state_.soft_memory_limit_in_bytes,
           global_state_.unused_memory_limit_in_bytes,
           global_state_.num_resources_limit);
     }