Fix for bug 287461. Caret Browsing is hardbound to the F7 key and is unable to be overridden with javascript like F3, F5, etc.

r+sr=neil patch by Brian King <brian@mozdev.org>

toolkit/content/widgets/browser.xml

@@ -813,9 +813,9 @@
     </implementation>
 
     <handlers>
-      <handler event="keypress" keycode="VK_F7">
+      <handler event="keypress" keycode="VK_F7" group="system">
         <![CDATA[
-          if (!event.isTrusted)
+          if (event.getPreventDefault() || !event.isTrusted)
             return;
 
           // Toggle browse with caret mode

xpfe/global/resources/content/bindings/browser.xml

@@ -395,9 +395,9 @@
     </implementation>
 
     <handlers>
-      <handler event="keypress" keycode="VK_F7">
+      <handler event="keypress" keycode="VK_F7" group="system">
         <![CDATA[
-          if (!event.isTrusted)
+          if (event.getPreventDefault() || !event.isTrusted)
             return;
 
           // Toggle browse with caret mode