--- a/xpcom/tests/unit/test_file_createUnique.js
+++ b/xpcom/tests/unit/test_file_createUnique.js
@@ -17,13 +17,16 @@ function run_test()
                  getService(Ci.nsIProperties).get("TmpD", Ci.nsIFile);
   tempFile.append(longLeafName);
   tempFile.append("test.txt");
 
   try {
     tempFile.createUnique(Ci.nsIFile.NORMAL_FILE_TYPE, 0o600);
     do_throw("Creating an item in a folder with a very long name should throw");
   }
-  catch (e if (e instanceof Ci.nsIException &&
-               e.result == Cr.NS_ERROR_FILE_UNRECOGNIZED_PATH)) {
+  catch (e) {
+    if (!(e instanceof Ci.nsIException &&
+          e.result == Cr.NS_ERROR_FILE_UNRECOGNIZED_PATH)) {
+      throw e;
+    }
     // We expect the function not to crash but to raise this exception.
   }
 }

--- a/xpcom/tests/unit/test_storagestream.js
+++ b/xpcom/tests/unit/test_storagestream.js
@@ -34,18 +34,22 @@ function test1()
   var sis =
       Cc["@mozilla.org/scriptableinputstream;1"]
         .createInstance(Ci.nsIScriptableInputStream);
   sis.init(inp2);
 
   var threw = false;
   try {
     sis.read(1);
-  } catch (ex if ex.result == Cr.NS_BASE_STREAM_WOULD_BLOCK) {
-    threw = true;
+  } catch (ex) {
+    if (ex.result == Cr.NS_BASE_STREAM_WOULD_BLOCK) {
+      threw = true;
+    } else {
+      throw ex;
+    }
   }
   do_check_true(threw);
 }
 
 /**
  * Checks that getting an input stream from a storage stream to which 0 bytes of
  * data have been explicitly written doesn't throw an exception.
  */

--- a/xpcom/tests/unit/test_streams.js
+++ b/xpcom/tests/unit/test_streams.js
@@ -125,33 +125,42 @@ function test_binary_streams() {
   
   // Test for invalid actions.
   os.close();
   is.close();
 
   try {
     os.writeBoolean(false);
     do_throw("Not reached!");
-  } catch (e if (e instanceof Ci.nsIException &&
-                 e.result == Cr.NS_BASE_STREAM_CLOSED)) {
+  } catch (e) {
+    if (!(e instanceof Ci.nsIException &&
+          e.result == Cr.NS_BASE_STREAM_CLOSED)) {
+      throw e;
+    }
     // do nothing
   }
 
   try {
     is.available();
     do_throw("Not reached!");
-  } catch (e if (e instanceof Ci.nsIException &&
-                 e.result == Cr.NS_BASE_STREAM_CLOSED)) {
+  } catch (e) {
+    if (!(e instanceof Ci.nsIException &&
+          e.result == Cr.NS_BASE_STREAM_CLOSED)) {
+      throw e;
+    }
     // do nothing
   }
 
   try {
     is.readBoolean();
     do_throw("Not reached!");
-  } catch (e if (e instanceof Ci.nsIException &&
-                 e.result == Cr.NS_ERROR_FAILURE)) {
+  } catch (e) {
+    if (!(e instanceof Ci.nsIException &&
+          e.result == Cr.NS_ERROR_FAILURE)) {
+      throw e;
+    }
     // do nothing
   }
 }
 
 function run_test() {
   test_binary_streams();
 }

--- a/xpcom/tests/unit/test_windows_registry.js
+++ b/xpcom/tests/unit/test_windows_registry.js
@@ -47,18 +47,20 @@ function run_test()
 function setup_test_run(testKey, keyName)
 {
     do_print("Setup test run");
     try {
         testKey.open(nsIWindowsRegKey.ROOT_KEY_CURRENT_USER, keyName, nsIWindowsRegKey.ACCESS_READ);
         do_print("Test key exists. Needs cleanup.");
         cleanup_test_run(testKey, keyName);
     }
-    catch (e if (e instanceof Ci.nsIException && e.result == Cr.NS_ERROR_FAILURE))
-    {
+    catch (e) {
+        if (!(e instanceof Ci.nsIException && e.result == Cr.NS_ERROR_FAILURE)) {
+            throw e;
+        }
     }
 
     testKey.create(nsIWindowsRegKey.ROOT_KEY_CURRENT_USER, keyName, nsIWindowsRegKey.ACCESS_ALL);
 }
 
 function test_writing_functions(testKey)
 {
     strictEqual(testKey.valueCount, 0);
@@ -101,35 +103,47 @@ function test_reading_functions(testKey)
     strictEqual( testKey.readBinaryValue(TESTDATA_BINARYNAME), TESTDATA_BINARYVALUE);
 }
 
 function test_invalidread_functions(testKey)
 {
     try {
         testKey.readIntValue(TESTDATA_STRNAME);
         do_throw("Reading an integer from a string registry value should throw.");
-    } catch (e if (e instanceof Ci.nsIException && e.result == Cr.NS_ERROR_FAILURE)) {
+    } catch (e) {
+        if (!(e instanceof Ci.nsIException && e.result == Cr.NS_ERROR_FAILURE)) {
+            throw e;
+        }
     }
 
     try {
         let val = testKey.readStringValue(TESTDATA_INTNAME);
         do_throw("Reading an string from an Int registry value should throw." + val);
-    } catch (e if (e instanceof Ci.nsIException && e.result == Cr.NS_ERROR_FAILURE)) {
+    } catch (e) {
+        if (!(e instanceof Ci.nsIException && e.result == Cr.NS_ERROR_FAILURE)) {
+            throw e;
+        }
     }
 
     try {
         testKey.readStringValue(TESTDATA_INT64NAME);
         do_throw("Reading an string from an Int64 registry value should throw.");
-    } catch (e if (e instanceof Ci.nsIException && e.result == Cr.NS_ERROR_FAILURE)) {
+    } catch (e) {
+        if (!(e instanceof Ci.nsIException && e.result == Cr.NS_ERROR_FAILURE)) {
+            throw e;
+        }
     }
 
     try {
         testKey.readStringValue(TESTDATA_BINARYNAME);
         do_throw("Reading a string from an Binary registry value should throw.");
-    } catch (e if (e instanceof Ci.nsIException && e.result == Cr.NS_ERROR_FAILURE)) {
+    } catch (e) {
+        if (!(e instanceof Ci.nsIException && e.result == Cr.NS_ERROR_FAILURE)) {
+            throw e;
+        }
     }
 
 }
 
 function test_childkey_functions(testKey)
 {
     strictEqual(testKey.childCount, 0);
     strictEqual(testKey.hasChild(TESTDATA_CHILD_KEY), false);

--- a/xpcom/tests/unit/test_windows_shortcut.js
+++ b/xpcom/tests/unit/test_windows_shortcut.js
@@ -47,20 +47,21 @@ function test_create_noargs(tempDir)
 
   let win = shortcutFile.QueryInterface(Ci.nsILocalFileWin);
 
   try
   {
     win.setShortcut();
     do_throw("Creating a shortcut with no args (no target) should throw");
   }
-  catch(e if (e instanceof Ci.nsIException
-             && e.result == Cr.NS_ERROR_FILE_TARGET_DOES_NOT_EXIST))
-  {
-
+  catch(e) {
+    if (!(e instanceof Ci.nsIException
+          && e.result == Cr.NS_ERROR_FILE_TARGET_DOES_NOT_EXIST)) {
+      throw e;
+    }
   }
 }
 
 function test_create_notarget(tempDir)
 {
   let shortcutFile = tempDir.clone();
   shortcutFile.append("shouldNeverExist2.lnk");
   shortcutFile.createUnique(Ci.nsIFile.NORMAL_FILE_TYPE, 0o666);
@@ -70,20 +71,21 @@ function test_create_notarget(tempDir)
   try
   {
     win.setShortcut(null,
                     do_get_cwd(),
                     "arg1 arg2",
                     "Shortcut with no target");
     do_throw("Creating a shortcut with no target should throw");
   }
-  catch(e if (e instanceof Ci.nsIException
-             && e.result == Cr.NS_ERROR_FILE_TARGET_DOES_NOT_EXIST))
-  {
-
+  catch(e) {
+    if (!(e instanceof Ci.nsIException
+          && e.result == Cr.NS_ERROR_FILE_TARGET_DOES_NOT_EXIST)) {
+      throw e;
+    }
   }
 }
 
 function test_create_targetonly(tempDir)
 {
   let shortcutFile = tempDir.clone();
   shortcutFile.append("createdShortcut.lnk");
   shortcutFile.createUnique(Ci.nsIFile.NORMAL_FILE_TYPE, 0o666);