Preliminary work for unprefixed MSE SourceBuffer.mode manipulation

public/platform/WebSourceBuffer.h

Index: public/platform/WebSourceBuffer.h
diff --git a/public/platform/WebSourceBuffer.h b/public/platform/WebSourceBuffer.h
index 6eceac62d1272c247a3b3ee99dcda22238166ec5..b8960df909d5a4444d35ee619d043ded6b410aab 100644
--- a/public/platform/WebSourceBuffer.h
+++ b/public/platform/WebSourceBuffer.h
@@ -37,8 +37,16 @@ namespace blink {
 
 class WebSourceBuffer {
 public:
+    enum AppendMode {
+        AppendModeSegments,
+        AppendModeSequence
+    };
+
     virtual ~WebSourceBuffer() { }
 
+    // FIXME: Remove default implementation once Chromium setMode() implementation has landed. See http://crbug.com/249422.
+    virtual bool setMode(AppendMode) { return true; }
+
     virtual WebTimeRanges buffered() = 0;
     virtual void append(const unsigned char* data, unsigned length) = 0;
     virtual void abort() = 0;