Bug 1755722 - Use viewport distance as the root margins for lazyload in EARLY_BETA_OR_EARLIER r=emilio

This is for experimenting the best value for the root margins.

Differential Revision: https://phabricator.services.mozilla.com/D138907

modules/libpref/init/StaticPrefList.yaml

@@ -2354,7 +2354,7 @@
 - name: dom.image-lazy-loading.root-margin.top
   type: float
 #if defined(EARLY_BETA_OR_EARLIER)
-  value: 500
+  value: 100 # 100%
 #else
   value: 300
 #endif
@@ -2362,13 +2362,17 @@
 
 - name: dom.image-lazy-loading.root-margin.top.percentage
   type: bool
+#if defined(EARLY_BETA_OR_EARLIER)
+  value: true
+#else
   value: false
+#endif
   mirror: always
 
 - name: dom.image-lazy-loading.root-margin.bottom
   type: float
 #if defined(EARLY_BETA_OR_EARLIER)
-  value: 500
+  value: 100 # 100%
 #else
   value: 300
 #endif
@@ -2376,13 +2380,17 @@
 
 - name: dom.image-lazy-loading.root-margin.bottom.percentage
   type: bool
+#if defined(EARLY_BETA_OR_EARLIER)
+  value: true
+#else
   value: false
+#endif
   mirror: always
 
 - name: dom.image-lazy-loading.root-margin.left
   type: float
 #if defined(EARLY_BETA_OR_EARLIER)
-  value: 500
+  value: 100 # 100%
 #else
   value: 300
 #endif
@@ -2390,13 +2398,17 @@
 
 - name: dom.image-lazy-loading.root-margin.left.percentage
   type: bool
+#if defined(EARLY_BETA_OR_EARLIER)
+  value: true
+#else
   value: false
+#endif
   mirror: always
 
 - name: dom.image-lazy-loading.root-margin.right
   type: float
 #if defined(EARLY_BETA_OR_EARLIER)
-  value: 500
+  value: 100 # 100%
 #else
   value: 300
 #endif
@@ -2404,7 +2416,11 @@
 
 - name: dom.image-lazy-loading.root-margin.right.percentage
   type: bool
+#if defined(EARLY_BETA_OR_EARLIER)
+  value: true
+#else
   value: false
+#endif
   mirror: always
 
 # Enable passing the "storage" option to indexedDB.open.