chrome.displaySource custom bindings

This patch introduces custom bindings for 'chrome.displaySource' API.
These are bindings for 'startSession', 'terminateSession' methods
and for the 'onSessionStarted', 'onSessionTerminated',
'onSessionErrorOccured' events.

The bindings should belong to render process (i.e. be custom) as:
1) they accept dom objects arguments (MediaStreamTrack)
2) for security reasons: to keep all protocols handling within sandbox

The abstract 'DisplaySourceSession' class is added to be implemented
by the 'chrome.displaySource' API backends.

BUG=242107

Review URL: https://codereview.chromium.org/1471243002

Cr-Commit-Position: refs/heads/master@{#364045}

1 files changed, 10 insertions, 3 deletions

diff --git a/extensions/common/api/display_source.idl b/extensions/common/api/display_source.idl
index a3821e3..f65a82a 100644
--- a/extensions/common/api/display_source.idl
+++ b/extensions/common/api/display_source.idl
@@ -89,7 +89,12 @@ namespace displaySource {
 
   callback GetSinksCallback = void (SinkInfo[] result);
   callback RequestAuthenticationCallback = void (AuthenticationInfo result);
-  callback TerminateSessionCallback = void ();
+
+  // The callback is used by <code>startSession, terminateSession</code>
+  // to signal completion. The callback is called with
+  // <code>chrome.runtime.lastError</code> set to error
+  // message if the call has failed.
+  [inline_doc] callback CallCompleteCallback = void ();
  
   interface Functions {
     // Queries the list of the currently available Display sinks.
@@ -123,13 +128,15 @@ namespace displaySource {
     // are required by the sink; otherwise its |data| field must contain the
     // required authentication data (e.g. PIN value) and its |method| field must
     // be the same as one obtained from ‘requestAuthentication’.
-    [nocompile] static void startSession(StartSessionInfo sessionInfo);
+    // |callback| : Called when the session is started.
+    [nocompile] static void startSession(
+        StartSessionInfo sessionInfo, optional CallCompleteCallback callback);
 
     // Terminates the active Display session.
     // |sinkId| : Id of the connected sink.
     // |callback| : Called when the session is terminated.
     [nocompile] static void terminateSession(
-        long sinkId, optional TerminateSessionCallback callback);
+        long sinkId, optional CallCompleteCallback callback);
   };
 
   interface Events {