Implements core logic for Pixel Canvas

ui/compositor/compositor.cc

Index: ui/compositor/compositor.cc
diff --git a/ui/compositor/compositor.cc b/ui/compositor/compositor.cc
index f0c88887bd3ff29000de140971798002e858e8c6..bc61e1d67dd86cf8b7d446b764309922a00e71f4 100644
--- a/ui/compositor/compositor.cc
+++ b/ui/compositor/compositor.cc
@@ -60,6 +60,7 @@ Compositor::Compositor(const viz::FrameSinkId& frame_sink_id,
                        ui::ContextFactoryPrivate* context_factory_private,
                        scoped_refptr<base::SingleThreadTaskRunner> task_runner,
                        bool enable_surface_synchronization,
+                       bool enable_pixel_canvas,
                        bool external_begin_frames_enabled)
     : context_factory_(context_factory),
       context_factory_private_(context_factory_private),
@@ -70,6 +71,7 @@ Compositor::Compositor(const viz::FrameSinkId& frame_sink_id,
       layer_animator_collection_(this),
       scheduled_timeout_(base::TimeTicks()),
       allow_locks_to_extend_timeout_(false),
+      is_pixel_canvas_(enable_pixel_canvas),
       weak_ptr_factory_(this),
       lock_timeout_weak_ptr_factory_(this) {
   if (context_factory_private) {
@@ -334,6 +336,8 @@ void Compositor::SetScaleAndSize(float scale, const gfx::Size& size_in_pixel) {
   if (device_scale_factor_ != scale) {
     device_scale_factor_ = scale;
     host_->SetDeviceScaleFactor(scale);
+    if (is_pixel_canvas())
+      host_->SetRecordingScaleFactor(scale);
     if (root_layer_)
       root_layer_->OnDeviceScaleFactorChanged(scale);
   }