Support enabling/disabling toggles in unittests

Refactors support for toggle control flags, --enable-toggles= &
--disable-toggles, from the end2end tests into a utility class to make
them available elsewhere. The unittests now uses this utility class to
parse toggle control flags.

For some toggles, like 'use_tint_generator', the unittests are known to
be broken with them turned on. They will be fixed in subsequent CLs.

BUG=dawn:756

Change-Id: Ic283e8a82bedcbf255258cca3e62f58c79d3857b
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/47740
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Commit-Queue: Corentin Wallez <cwallez@chromium.org>
Auto-Submit: Ryan Harrison <rharrison@chromium.org>
diff --git a/src/tests/ToggleParser.cpp b/src/tests/ToggleParser.cpp
new file mode 100644
index 0000000..3589aea
--- /dev/null
+++ b/src/tests/ToggleParser.cpp
@@ -0,0 +1,57 @@
+// Copyright 2021 The Dawn Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "tests/ToggleParser.h"
+
+#include <cstring>
+#include <sstream>
+
+ToggleParser::ToggleParser() = default;
+ToggleParser::~ToggleParser() = default;
+
+bool ToggleParser::ParseEnabledToggles(char* arg) {
+    constexpr const char kEnableTogglesSwitch[] = "--enable-toggles=";
+    size_t argLen = sizeof(kEnableTogglesSwitch) - 1;
+    if (strncmp(arg, kEnableTogglesSwitch, argLen) == 0) {
+        std::string toggle;
+        std::stringstream toggles(arg + argLen);
+        while (getline(toggles, toggle, ',')) {
+            mEnabledToggles.push_back(toggle);
+        }
+        return true;
+    }
+    return false;
+}
+
+bool ToggleParser::ParseDisabledToggles(char* arg) {
+    constexpr const char kDisableTogglesSwitch[] = "--disable-toggles=";
+    size_t argLDis = sizeof(kDisableTogglesSwitch) - 1;
+    if (strncmp(arg, kDisableTogglesSwitch, argLDis) == 0) {
+        std::string toggle;
+        std::stringstream toggles(arg + argLDis);
+        while (getline(toggles, toggle, ',')) {
+            mDisabledToggles.push_back(toggle);
+        }
+        return true;
+    }
+    return false;
+}
+
+const std::vector<std::string>& ToggleParser::GetEnabledToggles() const {
+    return mEnabledToggles;
+}
+
+const std::vector<std::string>& ToggleParser::GetDisabledToggles() const {
+    return mDisabledToggles;
+}