Bug 1906155 - Add pref webgl.1.request_es2:true. r=gfx-reviewers,lsalzman

Differential Revision: https://phabricator.services.mozilla.com/D215665

dom/canvas/WebGLContext.cpp

@@ -315,8 +315,10 @@ bool WebGLContext::CreateAndInitGL(
   if (IsWebGL2()) {
     flags |= gl::CreateContextFlags::PREFER_ES3;
   } else {
-    // Request and prefer ES2 context for WebGL1.
-    flags |= gl::CreateContextFlags::PREFER_EXACT_VERSION;
+    if (StaticPrefs::webgl_1_request_es2()) {
+      // Request and prefer ES2 context for WebGL1.
+      flags |= gl::CreateContextFlags::PREFER_EXACT_VERSION;
+    }
 
     if (!StaticPrefs::webgl_1_allow_core_profiles()) {
       flags |= gl::CreateContextFlags::REQUIRE_COMPAT_PROFILE;

modules/libpref/init/StaticPrefList.yaml

@@ -16143,6 +16143,11 @@
 #endif
   mirror: always
 
+- name: webgl.1.request_es2
+  type: RelaxedAtomicBool
+  value: true
+  mirror: always
+
 - name: webgl.angle.force-d3d11
   type: RelaxedAtomicBool
   value: false