LayerTreeHost should not modify the LayerTreeSettings object. Instead it should use a temporary va…

cc/trees/layer_tree_host.cc

Index: cc/trees/layer_tree_host.cc
diff --git a/cc/trees/layer_tree_host.cc b/cc/trees/layer_tree_host.cc
index e3a1b32924839b697d18d135ad0b816ef3711d81..13c0984c1ea07a0885de4b924aa2fc20fca8b46a 100644
--- a/cc/trees/layer_tree_host.cc
+++ b/cc/trees/layer_tree_host.cc
@@ -130,6 +130,7 @@ LayerTreeHost::LayerTreeHost(LayerTreeHostClient* client,
       background_color_(SK_ColorWHITE),
       has_transparent_background_(false),
       partial_texture_update_requests_(0),
+      max_partial_texture_updates_(settings_.max_partial_texture_updates),

[danakj, 2013/10/03 17:42:26]

Can we initialize this to 0?

       in_paint_layer_contents_(false),
       total_frames_used_for_lcd_text_metrics_(0),
       tree_id_(s_next_tree_id++) {
@@ -205,7 +206,7 @@ LayerTreeHost::OnCreateAndInitializeOutputSurfaceAttempted(bool success) {
   if (success) {
     output_surface_lost_ = false;
 
-    // Update settings_ based on partial update capability.
+    // Update max_partial_texture_updates_ based on partial update capability.
     size_t max_partial_texture_updates = 0;
     if (proxy_->GetRendererCapabilities().allow_partial_texture_updates &&
         !settings_.impl_side_painting) {
@@ -213,7 +214,7 @@ LayerTreeHost::OnCreateAndInitializeOutputSurfaceAttempted(bool success) {
           settings_.max_partial_texture_updates,
           proxy_->MaxPartialTextureUpdates());
     }
-    settings_.max_partial_texture_updates = max_partial_texture_updates;
+    max_partial_texture_updates_ = max_partial_texture_updates;
 
     if (!contents_texture_manager_ &&
         (!settings_.impl_side_painting || !settings_.solid_color_scrollbars)) {
@@ -1119,7 +1120,7 @@ void LayerTreeHost::RateLimit() {
 }
 
 bool LayerTreeHost::RequestPartialTextureUpdate() {
-  if (partial_texture_update_requests_ >= settings_.max_partial_texture_updates)
+  if (partial_texture_update_requests_ >= MaxPartialTextureUpdates())
     return false;
 
   partial_texture_update_requests_++;