Synchronously drop tile textures in android webview

cc/trees/layer_tree_host_impl.cc

Index: cc/trees/layer_tree_host_impl.cc
diff --git a/cc/trees/layer_tree_host_impl.cc b/cc/trees/layer_tree_host_impl.cc
index fa8c22011a956aa42425af3584f333fbd3a5bb0f..e350764ed66b0287be3c827ca32a12971f15555d 100644
--- a/cc/trees/layer_tree_host_impl.cc
+++ b/cc/trees/layer_tree_host_impl.cc
@@ -1327,6 +1327,17 @@ void LayerTreeHostImpl::NotifyTileStateChanged(const Tile* tile) {
 
 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.
+  // crbug.com/499004 to track removing this.
+  if (!policy.bytes_limit_when_visible && tile_manager_ &&
+      settings_.using_synchronous_renderer_compositor) {
+    ReleaseTreeResources();
+    DestroyTileManager();

[vmpstr, 2015/06/10 23:15:54]

Can you make a comment that explains that destruction of tile manager will
synchronously wait for all tiles to be canceled/completed.

Also, this doesn't do any flushes or anything like that, do we need that as
well?
 

[boliu, 2015/06/10 23:20:56]

Done
That was added last week in https://codereview.chromium.org/1162793005/ :)

+    CreateAndSetTileManager();
+    RecreateTreeResources();
+  }
 }
 
 void LayerTreeHostImpl::SetTreeActivationCallback(