Bug 1742203 - Tweak lazy-loading root margin defaults to 500px in all directions for EARLY_BETA_OR_EARLIER r=emilio

Differential Revision: https://phabricator.services.mozilla.com/D131713

modules/libpref/init/StaticPrefList.yaml

@@ -2321,7 +2321,7 @@
 - name: dom.image-lazy-loading.root-margin.top
   type: float
 #if defined(EARLY_BETA_OR_EARLIER)
-  value: 800
+  value: 500
 #else
   value: 300
 #endif
@@ -2335,7 +2335,7 @@
 - name: dom.image-lazy-loading.root-margin.bottom
   type: float
 #if defined(EARLY_BETA_OR_EARLIER)
-  value: 800
+  value: 500
 #else
   value: 300
 #endif
@@ -2349,7 +2349,7 @@
 - name: dom.image-lazy-loading.root-margin.left
   type: float
 #if defined(EARLY_BETA_OR_EARLIER)
-  value: 800
+  value: 500
 #else
   value: 300
 #endif
@@ -2363,7 +2363,7 @@
 - name: dom.image-lazy-loading.root-margin.right
   type: float
 #if defined(EARLY_BETA_OR_EARLIER)
-  value: 800
+  value: 500
 #else
   value: 300
 #endif