[Firefox] Handle the user modifying the "mousewheel.with_meta.action" and "mousewheel.with_control.action" prefs (bug 1170063)

Fixes https://bugzilla.mozilla.org/show_bug.cgi?id=1170063.

The bug only mentions the <kbd>Meta</kbd> key, but given that a similar situation can occur for <kbd>Ctrl</kbd>, it seemed reasonable to also handle that case in the same patch.

The only possible caveat with the patch is that because of the use of `shadow`, things won't work perfectly if either of the prefs are changed *while* the viewer is active. In this case a reload is required in order for it to work correctly, but given that the issue this patch fixes should be quite rare anyway, that seems OK.

extensions/firefox/content/PdfStreamConverter.jsm

@@ -423,6 +423,12 @@ ChromeActions.prototype = {
     }
     return true;
   },
+  supportedMouseWheelZoomModifierKeys: function() {
+    return {
+      ctrlKey: getIntPref('mousewheel.with_control.action', 3) === 3,
+      metaKey: getIntPref('mousewheel.with_meta.action', 1) === 3,
+    };
+  },
   reportTelemetry: function (data) {
     var probeInfo = JSON.parse(data);
     switch (probeInfo.type) {

web/viewer.js

@@ -394,6 +394,18 @@ var PDFViewerApplication = {
     return PDFJS.shadow(this, 'loadingBar', bar);
   },
 
+  get supportedMouseWheelZoomModifierKeys() {
+    var support = {
+      ctrlKey: true,
+      metaKey: true,
+    };
+//#if (FIREFOX || MOZCENTRAL)
+//  support = FirefoxCom.requestSync('supportedMouseWheelZoomModifierKeys');
+//#endif
+
+    return PDFJS.shadow(this, 'supportedMouseWheelZoomModifierKeys', support);
+  },
+
 //#if (FIREFOX || MOZCENTRAL)
   initPassiveLoading: function pdfViewInitPassiveLoading() {
     function FirefoxComDataRangeTransport(length, initialData) {
@@ -1845,6 +1857,11 @@ function handleMouseWheel(evt) {
     PDFViewerApplication.scrollPresentationMode(ticks *
                                                 MOUSE_WHEEL_DELTA_FACTOR);
   } else if (evt.ctrlKey || evt.metaKey) {
+    var support = PDFViewerApplication.supportedMouseWheelZoomModifierKeys;
+    if ((evt.ctrlKey && !support.ctrlKey) ||
+        (evt.metaKey && !support.metaKey)) {
+      return;
+    }
     // Only zoom the pages, not the entire viewer.
     evt.preventDefault();
     PDFViewerApplication[direction](Math.abs(ticks));