New SkRTConf macro SK_CONF_TRY_SET: no complaint on missing configuration

tests/RuntimeConfigTest.cpp

+/*
+ * Copyright 2013 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+#include "SkRTConf.h"
+#include "Test.h"
+#include "TestClassDef.h"
+
+SK_CONF_DECLARE(int, c_RTConfTestVariable,
+                "test.utils.rtconf.testVariable", 1,
+                "This is only a test. Do not be alarmed.");
+// TODO(skia-team): more comprehensive unit tests of the SkRTConf
+// system.
+DEF_TEST(RuntimeConfig, reporter) {
+    REPORTER_ASSERT(reporter, 1 == c_RTConfTestVariable);
+
+    SK_CONF_SET("test.utils.rtconf.testVariable", 2);
+#ifdef SK_DEVELOPER
+    REPORTER_ASSERT(reporter, 2 == c_RTConfTestVariable);
+#else  // not SK_DEVELOPER
+    // Can not change RTConf variables in Release.
+    REPORTER_ASSERT(reporter, 1 == c_RTConfTestVariable);
+#endif  // SK_DEVELOPER
+
+    // This should not give a warning.
+    SK_CONF_TRY_SET("test.utils.rtconf.nonexistentVariable", 7);
+}