impl default for canvas cache

examples/clock/src/main.rs

@@ -29,7 +29,7 @@ impl Application for Clock {
         (
             Clock {
                 now: chrono::Local::now().into(),
-                clock: canvas::layer::Cache::new(),
+                clock: Default::default(),
             },
             Command::none(),
         )

examples/solar_system/src/main.rs

@@ -39,7 +39,7 @@ impl Application for SolarSystem {
         (
             SolarSystem {
                 state: State::new(),
-                solar_system: canvas::layer::Cache::new(),
+                solar_system: Default::default(),
             },
             Command::none(),
         )