diff --git a/docshell/test/chrome/bug298622_window.xhtml b/docshell/test/chrome/bug298622_window.xhtml
index 5c95a9fed13b..e02ecc1f2d33 100644
--- a/docshell/test/chrome/bug298622_window.xhtml
+++ b/docshell/test/chrome/bug298622_window.xhtml
@@ -141,6 +141,6 @@
     <command id="cmd_find"
      oncommand="document.getElementById('FindToolbar').onFindCommand();"/>
   </commandset>
-  <browser type="content" primary="true" flex="1" id="content" src="about:blank"/>
+  <browser type="content" primary="true" flex="1" id="content" messagemanagergroup="test" src="about:blank"/>
   <findbar id="FindToolbar" browserid="content"/>
 </window>
diff --git a/docshell/test/chrome/bug301397_window.xhtml b/docshell/test/chrome/bug301397_window.xhtml
index 085db783c1d3..77c8f458cd33 100644
--- a/docshell/test/chrome/bug301397_window.xhtml
+++ b/docshell/test/chrome/bug301397_window.xhtml
@@ -244,5 +244,5 @@
     
   ]]></script>
 
-  <browser type="content" primary="true" flex="1" id="content" src="about:blank"/>
+  <browser type="content" primary="true" flex="1" id="content" messagemanagergroup="test" src="about:blank"/>
 </window>
diff --git a/toolkit/content/tests/chrome/bug263683_window.xhtml b/toolkit/content/tests/chrome/bug263683_window.xhtml
index 94f741a1a8a3..8111ac95a3ed 100644
--- a/toolkit/content/tests/chrome/bug263683_window.xhtml
+++ b/toolkit/content/tests/chrome/bug263683_window.xhtml
@@ -197,7 +197,7 @@
     }
   ]]></script>
 
-  <browser type="content" primary="true" flex="1" id="content" src="about:blank"/>
-  <browser type="content" primary="true" flex="1" id="content-remote" remote="true" src="about:blank"/>
+  <browser type="content" primary="true" flex="1" id="content" messagemanagergroup="test" src="about:blank"/>
+  <browser type="content" primary="true" flex="1" id="content-remote" remote="true" messagemanagergroup="test" src="about:blank"/>
   <findbar id="FindToolbar" browserid="content"/>
 </window>
diff --git a/toolkit/content/tests/chrome/bug304188_window.xhtml b/toolkit/content/tests/chrome/bug304188_window.xhtml
index 455fce1b74bf..b6fbee19a967 100644
--- a/toolkit/content/tests/chrome/bug304188_window.xhtml
+++ b/toolkit/content/tests/chrome/bug304188_window.xhtml
@@ -81,7 +81,7 @@ find-menu appears in editor element which has had makeEditable() called but desi
     }
   ]]></script>
 
-  <browser id="content" flex="1" src="about:blank" type="content" primary="true"/>
-  <browser id="content-remote" remote="true" flex="1" src="about:blank" type="content" primary="true"/>
+  <browser id="content" flex="1" src="about:blank" type="content" primary="true" messagemanagergroup="test"/>
+  <browser id="content-remote" remote="true" flex="1" src="about:blank" type="content" primary="true" messagemanagergroup="test"/>
   <findbar id="FindToolbar" browserid="content"/>
 </window>
diff --git a/toolkit/content/tests/chrome/bug331215_window.xhtml b/toolkit/content/tests/chrome/bug331215_window.xhtml
index 8cb7664f9f41..6da87a9fb6f4 100644
--- a/toolkit/content/tests/chrome/bug331215_window.xhtml
+++ b/toolkit/content/tests/chrome/bug331215_window.xhtml
@@ -92,7 +92,7 @@
   <commandset>
     <command id="cmd_find" oncommand="document.getElementById('FindToolbar').onFindCommand();"/>
   </commandset>
-  <browser type="content" primary="true" flex="1" id="content" src="about:blank"/>
-  <browser type="content" primary="true" flex="1" id="content-remote" remote="true" src="about:blank"/>
+  <browser type="content" primary="true" flex="1" id="content" messagemanagergroup="test" src="about:blank"/>
+  <browser type="content" primary="true" flex="1" id="content-remote" remote="true" messagemanagergroup="test" src="about:blank"/>
   <findbar id="FindToolbar" browserid="content"/>
 </window>
diff --git a/toolkit/content/tests/chrome/bug360437_window.xhtml b/toolkit/content/tests/chrome/bug360437_window.xhtml
index d2794a37c933..f460902bd02a 100644
--- a/toolkit/content/tests/chrome/bug360437_window.xhtml
+++ b/toolkit/content/tests/chrome/bug360437_window.xhtml
@@ -115,7 +115,7 @@
     }
   ]]></script>
   <html:input id="textbox"/>
-  <browser type="content" primary="true" flex="1" id="content" src="about:blank"/>
-  <browser type="content" primary="true" flex="1" id="content-remote" remote="true" src="about:blank"/>
+  <browser type="content" primary="true" flex="1" id="content" messagemanagergroup="test" src="about:blank"/>
+  <browser type="content" primary="true" flex="1" id="content-remote" remote="true" messagemanagergroup="test" src="about:blank"/>
   <findbar id="FindToolbar" browserid="content"/>
 </window>
diff --git a/toolkit/content/tests/chrome/bug409624_window.xhtml b/toolkit/content/tests/chrome/bug409624_window.xhtml
index 2a773f00ead6..f36c47d07df2 100644
--- a/toolkit/content/tests/chrome/bug409624_window.xhtml
+++ b/toolkit/content/tests/chrome/bug409624_window.xhtml
@@ -93,6 +93,6 @@
     SimpleTest.waitForFocus(startTest, window);
   ]]></script>
 
-  <browser type="content" primary="true" flex="1" id="content" src="about:blank"/>
+  <browser type="content" primary="true" flex="1" id="content" messagemanagergroup="test" src="about:blank"/>
   <findbar id="FindToolbar" browserid="content"/>
 </window>
diff --git a/toolkit/content/tests/chrome/bug429723_window.xhtml b/toolkit/content/tests/chrome/bug429723_window.xhtml
index 6fe5fe161755..06f38b0564d0 100644
--- a/toolkit/content/tests/chrome/bug429723_window.xhtml
+++ b/toolkit/content/tests/chrome/bug429723_window.xhtml
@@ -80,6 +80,6 @@
   <commandset>
     <command id="cmd_find" oncommand="document.getElementById('FindToolbar').onFindCommand();"/>
   </commandset>
-  <browser type="content" primary="true" flex="1" id="content" src="about:blank"/>
+  <browser type="content" primary="true" flex="1" id="content" messagemanagergroup="test" src="about:blank"/>
   <findbar id="FindToolbar" browserid="content"/>
 </window>
diff --git a/toolkit/content/tests/chrome/bug451540_window.xhtml b/toolkit/content/tests/chrome/bug451540_window.xhtml
index f5a996363f8d..382f0093ba47 100644
--- a/toolkit/content/tests/chrome/bug451540_window.xhtml
+++ b/toolkit/content/tests/chrome/bug451540_window.xhtml
@@ -247,7 +247,7 @@
     SimpleTest.waitForFocus(startTest, window);
   ]]></script>
 
-  <browser type="content" primary="true" flex="1" id="content" src="about:blank"/>
-  <browser type="content" primary="true" flex="1" id="content-remote" remote="true" src="about:blank"/>
+  <browser type="content" primary="true" flex="1" id="content" messagemanagergroup="test" src="about:blank"/>
+  <browser type="content" primary="true" flex="1" id="content-remote" remote="true" messagemanagergroup="test" src="about:blank"/>
   <findbar id="FindToolbar" browserid="content"/>
 </window>
diff --git a/toolkit/content/tests/chrome/findbar_entireword_window.xhtml b/toolkit/content/tests/chrome/findbar_entireword_window.xhtml
index 73191ec98aec..e3f24462128d 100644
--- a/toolkit/content/tests/chrome/findbar_entireword_window.xhtml
+++ b/toolkit/content/tests/chrome/findbar_entireword_window.xhtml
@@ -263,7 +263,7 @@
   <commandset>
     <command id="cmd_find" oncommand="document.getElementById('FindToolbar').onFindCommand();"/>
   </commandset>
-  <browser type="content" primary="true" flex="1" id="content" src="about:blank"/>
-  <browser type="content" primary="true" flex="1" id="content-remote" remote="true" src="about:blank"/>
+  <browser type="content" primary="true" flex="1" id="content" messagemanagergroup="test" src="about:blank"/>
+  <browser type="content" primary="true" flex="1" id="content-remote" remote="true" messagemanagergroup="test" src="about:blank"/>
   <findbar id="FindToolbar" browserid="content"/>
 </window>
diff --git a/toolkit/content/tests/chrome/findbar_events_window.xhtml b/toolkit/content/tests/chrome/findbar_events_window.xhtml
index 27cb9a3316cf..b8e84cee4102 100644
--- a/toolkit/content/tests/chrome/findbar_events_window.xhtml
+++ b/toolkit/content/tests/chrome/findbar_events_window.xhtml
@@ -183,7 +183,7 @@
     }
   ]]></script>
 
-  <browser type="content" primary="true" flex="1" id="content" src="about:blank"/>
-  <browser type="content" primary="true" flex="1" id="content-remote" remote="true" src="about:blank"/>
+  <browser type="content" primary="true" flex="1" id="content" messagemanagergroup="test" src="about:blank"/>
+  <browser type="content" primary="true" flex="1" id="content-remote" remote="true" messagemanagergroup="test" src="about:blank"/>
   <findbar id="FindToolbar" browserid="content"/>
 </window>
diff --git a/toolkit/content/tests/chrome/findbar_window.xhtml b/toolkit/content/tests/chrome/findbar_window.xhtml
index a280f2230c2e..6fc38acf691e 100644
--- a/toolkit/content/tests/chrome/findbar_window.xhtml
+++ b/toolkit/content/tests/chrome/findbar_window.xhtml
@@ -779,7 +779,7 @@
   <commandset>
     <command id="cmd_find" oncommand="document.getElementById('FindToolbar').onFindCommand();"/>
   </commandset>
-  <browser type="content" primary="true" flex="1" id="content" src="about:blank"/>
-  <browser type="content" primary="true" flex="1" id="content-remote" remote="true" src="about:blank"/>
+  <browser type="content" primary="true" flex="1" id="content" messagemanagergroup="test" src="about:blank"/>
+  <browser type="content" primary="true" flex="1" id="content-remote" remote="true" messagemanagergroup="test" src="about:blank"/>
   <findbar id="FindToolbar" browserid="content"/>
 </window>
diff --git a/toolkit/modules/ActorManagerParent.jsm b/toolkit/modules/ActorManagerParent.jsm
index 860bec9a39c0..10d6129cfc70 100644
--- a/toolkit/modules/ActorManagerParent.jsm
+++ b/toolkit/modules/ActorManagerParent.jsm
@@ -180,6 +180,7 @@ let ACTORS = {
     },
 
     allFrames: true,
+    messageManagerGroups: ["browsers", "test"],
   },
 
   // This is the actor that responds to requests from the find toolbar and