Improve detection of touch events when hiding media controls.

Source/platform/PlatformMouseEvent.h

Index: Source/platform/PlatformMouseEvent.h
diff --git a/Source/platform/PlatformMouseEvent.h b/Source/platform/PlatformMouseEvent.h
index 4a4b8a95ee4539a6f39e03ce151b885fb093e07c..ba0171ee1570bab4e008b47f50135229c16f68f8 100644
--- a/Source/platform/PlatformMouseEvent.h
+++ b/Source/platform/PlatformMouseEvent.h
@@ -91,6 +91,7 @@ public:
     int clickCount() const { return m_clickCount; }
     unsigned modifierFlags() const { return m_modifierFlags; }
     bool fromTouch() const { return m_synthesized == FromTouch; }
+    SyntheticEventType syntheticEventType() const { return m_synthesized; }
 
 protected:
     IntPoint m_position;