Introduce painted-device-scale-factor and use it when --enable-use-zoom-for-dsf is specified.

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 1a5177112af55d73bff1637492a1cb89cfcb4c05..c69db831001b9d4b73912066b014494317194e5c 100644
--- a/cc/trees/layer_tree_host.cc
+++ b/cc/trees/layer_tree_host.cc
@@ -99,6 +99,7 @@ LayerTreeHost::LayerTreeHost(InitParams* params)
       top_controls_height_(0.f),
       top_controls_shown_ratio_(0.f),
       device_scale_factor_(1.f),
+      painted_device_scale_factor_(0.f),

[danakj, 2015/10/22 23:15:29]

default to 1?

[oshima, 2015/10/23 18:05:36]

I was using 0.f as a way to tell if which should be used. I changed the way you
suggested.

       visible_(false),
       page_scale_factor_(1.f),
       min_page_scale_factor_(1.f),
@@ -311,6 +312,7 @@ void LayerTreeHost::FinishCommitOnImplThread(LayerTreeHostImpl* host_impl) {
   // properties are set, since those trigger an update of GPU rasterization
   // status, which depends on the device scale factor. (crbug.com/535700)
   sync_tree->SetDeviceScaleFactor(device_scale_factor_);
+  sync_tree->SetPaintedDeviceScaleFactor(painted_device_scale_factor_);
   host_impl->SetDebugState(debug_state_);
   if (pending_page_scale_animation_) {
     sync_tree->SetPendingPageScaleAnimation(
@@ -588,7 +590,6 @@ void LayerTreeHost::SetHasGpuRasterizationTrigger(bool has_trigger) {
 void LayerTreeHost::SetViewportSize(const gfx::Size& device_viewport_size) {
   if (device_viewport_size == device_viewport_size_)
     return;
-

[danakj, 2015/10/22 23:15:29]

unrelated change

[oshima, 2015/10/23 18:05:36]

Done.

   device_viewport_size_ = device_viewport_size;
 
   SetPropertyTreesNeedRebuild();
@@ -871,6 +872,16 @@ void LayerTreeHost::SetDeviceScaleFactor(float device_scale_factor) {
   SetNeedsCommit();
 }
 
+void LayerTreeHost::SetPaintedDeviceScaleFactor(
+    float painted_device_scale_factor) {
+  if (painted_device_scale_factor == painted_device_scale_factor_)
+    return;
+  painted_device_scale_factor_ = painted_device_scale_factor;
+
+  property_trees_.needs_rebuild = true;

[danakj, 2015/10/22 23:15:29]

i don't think this is true, it's not used in property trees

[oshima, 2015/10/23 18:05:36]

Done.

+  SetNeedsCommit();
+}
+
 void LayerTreeHost::UpdateTopControlsState(TopControlsState constraints,
                                            TopControlsState current,
                                            bool animate) {