Bug 948465 - Part 1: Register resource://android/ pointing to Fennec APK root. r=mfinkle

Consumers can access Android assets (and resources) by using
resource://android/assets/FILENAME.

The resource substitution is registered at app-startup time so that the
substitution is in place before any add-on has started up: as documented
at [1], "[an] add-on will not receive xpcom-startup or app-startup
notifications".

[1] https://developer.mozilla.org/en-US/docs/Mozilla/Tech/XPCOM/Guide/Receiving_startup_notifications

mobile/android/components/BrowserCLH.js

@@ -119,8 +119,33 @@ BrowserCLH.prototype = {
     }
   },
 
+  /**
+   * Register resource://android as the APK root.
+   *
+   * Consumers can access Android assets using resource://android/assets/FILENAME.
+   */
+  setResourceSubstitutions: function () {
+    let registry = Cc["@mozilla.org/chrome/chrome-registry;1"].getService(Ci["nsIChromeRegistry"]);
+    // Like jar:jar:file:///data/app/org.mozilla.fennec-2.apk!/assets/omni.ja!/chrome/chrome/content/aboutHome.xhtml
+    let url = registry.convertChromeURL(Services.io.newURI("chrome://browser/content/aboutHome.xhtml", null, null)).spec;
+    // Like jar:file:///data/app/org.mozilla.fennec-2.apk!/
+    url = url.substring(4, url.indexOf("!/") + 2);
+
+    let protocolHandler = Services.io.getProtocolHandler("resource").QueryInterface(Ci.nsIResProtocolHandler);
+    protocolHandler.setSubstitution("android", Services.io.newURI(url, null, null));
+  },
+
+  observe: function (subject, topic, data) {
+    switch (topic) {
+      case "app-startup":
+        this.setResourceSubstitutions();
+        break;
+    }
+  },
+
   // QI
-  QueryInterface: XPCOMUtils.generateQI([Ci.nsICommandLineHandler]),
+  QueryInterface: XPCOMUtils.generateQI([Ci.nsICommandLineHandler,
+                                         Ci.nsIObserver]),
 
   // XPCOMUtils factory
   classID: Components.ID("{be623d20-d305-11de-8a39-0800200c9a66}")

mobile/android/components/MobileComponents.manifest

@@ -66,6 +66,7 @@ category wakeup-request PromptService @mozilla.org/embedcomp/prompt-service;1,ns
 component {be623d20-d305-11de-8a39-0800200c9a66} BrowserCLH.js application={aa3c5121-dab2-40e2-81ca-7ea25febc110}
 contract @mozilla.org/browser/browser-clh;1 {be623d20-d305-11de-8a39-0800200c9a66}
 category command-line-handler x-browser @mozilla.org/browser/browser-clh;1
+category app-startup BrowserCLH @mozilla.org/browser/browser-clh;1
 
 # ContentDispatchChooser.js
 component {5a072a22-1e66-4100-afc1-07aed8b62fc5} ContentDispatchChooser.js