Implement break signal for serial api.

extensions/common/api/serial.idl

Index: extensions/common/api/serial.idl
diff --git a/extensions/common/api/serial.idl b/extensions/common/api/serial.idl
index d5bbc02aca2496ee770b304817721446dda67585..dae1135759778fd90cecbbe059251476d24e572b 100644
--- a/extensions/common/api/serial.idl
+++ b/extensions/common/api/serial.idl
@@ -171,6 +171,10 @@ namespace serial {
 
   callback FlushCallback = void (boolean result);
 
+  callback SetBreakCallback = void (boolean result);
+
+  callback ClearBreakCallback = void (boolean result);
+
   // The set of control signals which may be sent to a connected serial device
   // using <code>setControlSignals</code>. Note that support for these signals
   // is device-dependent.
@@ -307,6 +311,16 @@ namespace serial {
     static void setControlSignals(long connectionId,
                                   HostControlSignals signals,
                                   SetControlSignalsCallback callback);
+
+    // Suspends character transmission on a given connection and places the
+    // transmission line in a break state until the clearBreak is called.
+    // |connectionId| : The id of the connection.
+    static void setBreak(long connectionId, SetBreakCallback callback);
+
+    // Restore character transmission on a given connection and place the
+    // transmission line in a nonbreak state.
+    // |connectionId| : The id of the connection.
+    static void clearBreak(long connectionId, ClearBreakCallback callback);
   };
 
   interface Events {