Bug 532146 - NetUtil.jsm needs a helper for creating new channels

Adds a new method for creating an nsIChannel from a string spec, an nsIURI, or
an nsIFile.
r=bz
sr=vlad

netwerk/base/src/NetUtil.jsm

@@ -204,6 +204,41 @@ const NetUtil = {
         return this.ioService.newURI(aTarget, aOriginCharset, aBaseURI);
     },
 
+    /**
+     * Constructs a new channel for the given spec, character set, and base URI,
+     * or nsIURI, or nsIFile.
+     *
+     * @param aWhatToLoad
+     *        The string spec for the desired URI, an nsIURI, or an nsIFile.
+     * @param aOriginCharset [optional]
+     *        The character set for the URI.  Only used if aWhatToLoad is a
+     *        string.
+     * @param aBaseURI [optional]
+     *        The base URI for the spec.  Only used if aWhatToLoad is a string.
+     *
+     * @return an nsIChannel object.
+     */
+    newChannel: function NetUtil_newChannel(aWhatToLoad, aOriginCharset,
+                                            aBaseURI)
+    {
+        if (!aWhatToLoad) {
+            let exception = new Components.Exception(
+                "Must have a non-null string spec, nsIURI, or nsIFile object",
+                Cr.NS_ERROR_INVALID_ARG,
+                Components.stack.caller
+            );
+            throw exception;
+        }
+
+        let uri = aWhatToLoad;
+        if (!(aWhatToLoad instanceof Ci.nsIURI)) {
+            // We either have a string or an nsIFile that we'll need a URI for.
+            uri = this.newURI(aWhatToLoad, aOriginCharset, aBaseURI);
+        }
+
+        return this.ioService.newChannelFromURI(uri);
+    },
+
     /**
      * Returns a reference to nsIIOService.
      *

netwerk/test/unit/test_NetUtil.js

@@ -286,6 +286,64 @@ function test_asyncFetch_does_not_block()
   });
 }
 
+function test_newChannel_no_specifier()
+{
+  try {
+    NetUtil.newChannel();
+    do_throw("should throw!");
+  }
+  catch (e) {
+    do_check_eq(e.result, Cr.NS_ERROR_INVALID_ARG);
+  }
+
+  run_next_test();
+}
+
+function test_newChannel_with_string()
+{
+  const TEST_SPEC = "http://mozilla.org";
+
+  // Check that we get the same URI back from channel the IO service creates and
+  // the channel the utility method creates.
+  let ios = NetUtil.ioService;
+  let iosChannel = ios.newChannel(TEST_SPEC, null, null);
+  let NetUtilChannel = NetUtil.newChannel(TEST_SPEC);
+  do_check_true(iosChannel.URI.equals(NetUtilChannel.URI));
+
+  run_next_test();
+}
+
+function test_newChannel_with_nsIURI()
+{
+  const TEST_SPEC = "http://mozilla.org";
+
+  // Check that we get the same URI back from channel the IO service creates and
+  // the channel the utility method creates.
+  let uri = NetUtil.newURI(TEST_SPEC);
+  let iosChannel = NetUtil.ioService.newChannelFromURI(uri);
+  let NetUtilChannel = NetUtil.newChannel(uri);
+  do_check_true(iosChannel.URI.equals(NetUtilChannel.URI));
+
+  run_next_test();
+}
+
+function test_newChannel_with_nsIFile()
+{
+  let file = Cc["@mozilla.org/file/directory_service;1"].
+             getService(Ci.nsIProperties).
+             get("TmpD", Ci.nsIFile);
+  file.append("NetUtil-test-file.tmp");
+
+  // Check that we get the same URI back from channel the IO service creates and
+  // the channel the utility method creates.
+  let uri = NetUtil.newURI(file);
+  let iosChannel = NetUtil.ioService.newChannelFromURI(uri);
+  let NetUtilChannel = NetUtil.newChannel(uri);
+  do_check_true(iosChannel.URI.equals(NetUtilChannel.URI));
+
+  run_next_test();
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 //// Test Runner
 
@@ -300,6 +358,10 @@ let tests = [
   test_asyncFetch_no_callback,
   test_asyncFetch,
   test_asyncFetch_does_not_block,
+  test_newChannel_no_specifier,
+  test_newChannel_with_string,
+  test_newChannel_with_nsIURI,
+  test_newChannel_with_nsIFile,
 ];
 let index = 0;