Bug 1507495, Enable Pointer events on GeckoView by default, r=droeh

Differential Revision: https://phabricator.services.mozilla.com/D38528

--HG--
extra : moz-landing-system : lando

mobile/android/chrome/geckoview/geckoview.js

@@ -431,6 +431,10 @@ function createBrowser() {
   const settings = window.arguments[0].QueryInterface(Ci.nsIAndroidView)
     .initData.settings;
   if (settings.useMultiprocess) {
+    if (Services.prefs
+          .getBoolPref("dom.w3c_pointer_events.multiprocess.android.enabled")) {
+      Services.prefs.setBoolPref("dom.w3c_pointer_events.enabled", true);
+    }
     browser.setAttribute("remote", "true");
     browser.setAttribute("remoteType", E10SUtils.DEFAULT_REMOTE_TYPE);
   }

modules/libpref/init/StaticPrefList.yaml

@@ -2018,6 +2018,13 @@
   value: -1
   mirror: always
 
+# If the pref is set to true, pointer events are enabled on GeckoView, but only
+# in the case it is using separate child processes.
+- name: dom.w3c_pointer_events.multiprocess.android.enabled
+  type: bool
+  value: true
+  mirror: always
+
 # Is support for Navigator.webdriver enabled?
 - name: dom.webdriver.enabled
   type: bool