Bug 1389380 - Add a test for storage pressure event; r=janv

A storage pressure event should be fired when the current usage is greater than
the global limit. Currently, the QuotaManger checks the usage and the limit in
two different cases, and this test verfiies both cases do fire a storage
pressure event with a correct value of usage. The first one is that a quota
client is asking for writting a new storage into the disk, but it will
make the currnet usage become greater than the global limit. The other one is
that the calculating limit is less than the current usage while initilaizing the
temporary storage.

--HG--
extra : rebase_source : 0ce65ee177175462ac8928f70972699c428a1135

dom/quota/test/unit/head.js

@@ -9,6 +9,8 @@ const NS_ERROR_UNEXPECTED = Cr.NS_ERROR_UNEXPECTED;
 const NS_ERROR_STORAGE_BUSY = Cr.NS_ERROR_STORAGE_BUSY;
 const NS_ERROR_FILE_NO_DEVICE_SPACE = Cr.NS_ERROR_FILE_NO_DEVICE_SPACE;
 
+Cu.import("resource://gre/modules/Services.jsm");
+
 function is(a, b, msg)
 {
   Assert.equal(a, b, msg);

dom/quota/test/unit/test_storagePressure.js

@@ -0,0 +1,116 @@
+/**
+ * Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+function awaitStoragePressure()
+{
+  let promise_resolve;
+
+  let promise = new Promise(function(resolve) {
+    promise_resolve = resolve;
+  });
+
+  function observer(subject, topic) {
+    ok(true, "Got the storage pressure event");
+
+    Services.obs.removeObserver(observer, topic);
+
+    let usage = subject.QueryInterface(Ci.nsISupportsPRUint64).data;
+    promise_resolve(usage);
+  }
+
+  Services.obs.addObserver(observer, "QuotaManager::StoragePressure", false);
+
+  return promise;
+}
+
+/**
+ * This test is mainly to verify that the storage pressure event is fired when
+ * the eviction process is not able to free some space when a quota client
+ * attempts to write over the global limit or when the global limit is reduced
+ * below the global usage.
+ */
+
+async function testSteps()
+{
+  const globalLimitKB = 2;
+
+  const principal = getPrincipal("https://example.com");
+
+  info("Setting limits");
+
+  setGlobalLimit(globalLimitKB);
+
+  let request = initTemporaryStorage();
+  await requestFinished(request);
+
+  info("Persisting and filling an origin");
+
+  // We need to persist the origin first to omit the group limit checks.
+  // Otherwise, we would have to fill five separate origins.
+  request = persist(principal);
+  await requestFinished(request);
+
+  let database = getSimpleDatabase(principal);
+
+  request = database.open("data");
+  await requestFinished(request);
+
+  try {
+    request = database.write(getBuffer(globalLimitKB * 1024));
+    await requestFinished(request);
+
+    ok(true, "Should not have thrown");
+  } catch(ex) {
+    ok(false, "Should not have thrown");
+  }
+
+  info("Testing storage pressure by writing over the global limit");
+
+  info("Storing one more byte to get the storage pressure event while writing");
+
+  let promiseStoragePressure = awaitStoragePressure();
+
+  try {
+    request = database.write(getBuffer(1));
+    await requestFinished(request);
+
+    ok(false, "Should have thrown");
+  } catch(ex) {
+    ok(true, "Should have thrown");
+    ok(ex === NS_ERROR_FILE_NO_DEVICE_SPACE, "Threw right code");
+  }
+
+  info("Checking the storage pressure event");
+
+  let usage = await promiseStoragePressure;
+  ok(usage == globalLimitKB * 1024, "Got correct usage");
+
+  info("Testing storage pressure by reducing the global limit");
+
+  info("Reducing the global limit to get the storage pressuse event while the" +
+       " temporary storage is being initialized");
+
+  setGlobalLimit(globalLimitKB - 1);
+
+  request = reset();
+  await requestFinished(request);
+
+  promiseStoragePressure = awaitStoragePressure();
+
+  request = initTemporaryStorage();
+  await requestFinished(request);
+
+  info("Checking the storage pressure event");
+
+  usage = await promiseStoragePressure;
+  ok(usage == globalLimitKB * 1024, "Got correct usage");
+
+  info("Resetting limits");
+
+  resetGlobalLimit();
+
+  request = reset();
+  await requestFinished(request);
+}

dom/quota/test/unit/xpcshell.ini

@@ -37,6 +37,7 @@ support-files =
 [test_removeLocalStorage.js]
 [test_simpledb.js]
 [test_storagePersistentUpgrade.js]
+[test_storagePressure.js]
 [test_tempMetadataCleanup.js]
 [test_unknownFiles.js]
 [test_version2_1upgrade.js]