Bug 1822955 - Disable mozImageSmoothingEnabled by default. r=emilio

Differential Revision: https://phabricator.services.mozilla.com/D172860

dom/webidl/CanvasRenderingContext2D.webidl

@@ -46,6 +46,7 @@ interface CanvasRenderingContext2D {
   // image smoothing mode -- if disabled, images won't be smoothed
   // if scaled.
   [Deprecated="PrefixedImageSmoothingEnabled",
+   Pref="dom.mozImageSmoothingEnabled.enabled",
    BinaryName="imageSmoothingEnabled"]
   attribute boolean mozImageSmoothingEnabled;
 

modules/libpref/init/StaticPrefList.yaml

@@ -2158,6 +2158,12 @@
 # Prefs starting with "dom."
 #---------------------------------------------------------------------------
 
+# Whether CanvasRenderingContext2D.mozImageSmoothingEnabled is enabled.
+- name: dom.mozImageSmoothingEnabled.enabled
+  type: bool
+  value: false
+  mirror: always
+
 # Allow cut/copy
 - name: dom.allow_cut_copy
   type: bool