Synchronously drop tile textures in android webview

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 <map>
 #include <set>
@@ skipping 1309 matching lines @@
   // Check for a non-null active tree to avoid doing this during shutdown.
   if (active_tree_ && !client_->IsInsideDraw() && tile->required_for_draw()) {
     // The LayerImpl::NotifyTileStateChanged() should damage the layer, so this
     // redraw will make those tiles be displayed.
     SetNeedsRedraw();
   }
 }
 
 void LayerTreeHostImpl::SetMemoryPolicy(const ManagedMemoryPolicy& policy) {
   SetManagedMemoryPolicy(policy);
+
+  // This is short term solution to synchronously drop tile resources when
+  // using synchronous compositing to avoid memory usage regression.
+  // TODO(boliu): crbug.com/499004 to track removing this.
+  if (!policy.bytes_limit_when_visible && tile_manager_ &&
+      settings_.using_synchronous_renderer_compositor) {
+    ReleaseTreeResources();
+    // TileManager destruction will synchronoulsy wait for all tile workers to
+    // be cancelled or completed. This allows all resources to be freed
+    // synchronously.
+    DestroyTileManager();
+    CreateAndSetTileManager();
+    RecreateTreeResources();
+  }
 }
 
 void LayerTreeHostImpl::SetTreeActivationCallback(
     const base::Closure& callback) {
   DCHECK(proxy_->IsImplThread());
   DCHECK(settings_.impl_side_painting || callback.is_null());
   tree_activation_callback_ = callback;
 }
 
 void LayerTreeHostImpl::SetManagedMemoryPolicy(
@@ skipping 2143 matching lines @@
   new_target.SetToMin(layer_impl->MaxScrollOffset());
 
   curve->UpdateTarget(
       animation->TrimTimeToCurrentIteration(CurrentBeginFrameArgs().frame_time)
           .InSecondsF(),
       new_target);
 
   return true;
 }
 }  // namespace cc