Bug 1279108 - Disable leak detection for updater xpcshell tests. r=mccr8

With more recent version of ASAN, the updater program shows multiple
leaks, for different reasons.

One is that the updater code heavily relies on pointers into a large
buffer, with exceptions, making things difficult to avoid leaks of those
exceptions. At least it requires more effort than I'm willing to put for
the sake of upgrading the compiler we use for ASAN.

Another is that the leak suppressions are not currently used for
xpcshell tests, and some leaks attributed to libglib, that would
normally be suppressed, are not.

Moreover, even if the suppressions were used, it looks like some are not
rooted to already suppressed system libraries, and would require
investigation. Ideally, we'd have debug symbols installed for the system
libraries and would have full stack traces, but we don't, so this makes
the whole process harder than necessary.

All in all, the updater is a separate short-lived program, and until we
can address all the problems above, we can just ignore memory leaks in
it (which aren't new anyways and are ignored by not being detected by
the ASAN currently used on automation). We don't disable ASAN entirely,
though, only leak detection, and only for the updater program.

toolkit/mozapps/update/tests/data/xpcshellUtilsAUS.js

@@ -1783,11 +1783,28 @@ function runUpdateUsingUpdater(aExpectedStatus, aSwitchApp, aExpectedExitValue)
   args = args.concat(gCallbackArgs);
   debugDump("running the updater: " + updateBin.path + " " + args.join(" "));
 
+  // See bug 1279108.
+  // nsIProcess doesn't have an API to pass a separate environment to the
+  // subprocess, so we need to alter the environment of the current process
+  // before launching the updater binary.
+  let env = Cc["@mozilla.org/process/environment;1"].
+            getService(Ci.nsIEnvironment);
+  let asan_options = null;
+  if (env.exists("ASAN_OPTIONS")) {
+    asan_options = env.get("ASAN_OPTIONS");
+    env.set("ASAN_OPTIONS", asan_options + ":detect_leaks=0")
+  } else {
+    env.set("ASAN_OPTIONS", "detect_leaks=0")
+  }
+
   let process = Cc["@mozilla.org/process/util;1"].
                 createInstance(Ci.nsIProcess);
   process.init(updateBin);
   process.run(true, args, args.length);
 
+  // Restore previous ASAN_OPTIONS if there were any.
+  env.set("ASAN_OPTIONS", asan_options ? asan_options : "");
+
   let status = readStatusFile();
   if (process.exitValue != aExpectedExitValue || status != aExpectedStatus) {
     if (process.exitValue != aExpectedExitValue) {