Implement autoplay gesture override experiment.

Source/core/html/AutoplayExperimentConfig.h

Index: Source/core/html/AutoplayExperimentConfig.h
diff --git a/Source/core/html/AutoplayExperimentConfig.h b/Source/core/html/AutoplayExperimentConfig.h
new file mode 100644
index 0000000000000000000000000000000000000000..d49d9a394b023a12d7d194428d89d13c71b66786
--- /dev/null
+++ b/Source/core/html/AutoplayExperimentConfig.h
@@ -0,0 +1,46 @@
+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef AutoplayExperimentConfig_h
+#define AutoplayExperimentConfig_h
+
+#include "wtf/text/WTFString.h"

[philipj_slow, 2015/09/02 09:24:11]

Looks like this can be forward declared.

[liberato (no reviews please), 2015/09/04 06:49:45]

Done.

+
+namespace blink {
+
+// This must be kept in sync with WebSettings::AutoplayExperimentMode.
+// See WebSettings.h for documentation.
+class AutoplayExperimentConfig {
+    public:
+    enum Mode {
+        // Do not enable the autoplay experiment.
+        Off        = 0,
+        // Enable gestureless autoplay.
+        Enabled    = 1 << 0,
+        // Restrict gestureless autoplay to media that is visible in
+        // the viewport.
+        IfViewport = 1 << 1,
+        // Restrict gestureless autoplay to audio-less or muted media.
+        IfMuted    = 1 << 2,
+        // Restrict gestureless autoplay to sites which contain the
+        // viewport tag.
+        IfMobile   = 1 << 3,
+        // If gestureless autoplay is allowed, then mute the media before
+        // starting to play.
+        PlayMuted  = 1 << 4,
+    };
+
+    static Mode fromString(const String& token);
+};
+
+inline AutoplayExperimentConfig::Mode& operator|=(AutoplayExperimentConfig::Mode& a, const AutoplayExperimentConfig::Mode& b)
+{
+    a = static_cast<AutoplayExperimentConfig::Mode>(
+        static_cast<int>(a) | static_cast<int>(b));
+    return a;
+}
+
+} // namespace blink
+
+#endif // AutoplayExperimentConfig_h