[Telemetry] Refactor Chrome devtools tracing

tools/telemetry/telemetry/internal/platform/tracing_agent/chrome_tracing_devtools_manager.py

Index: tools/telemetry/telemetry/internal/platform/tracing_agent/chrome_tracing_devtools_manager.py
diff --git a/tools/telemetry/telemetry/internal/platform/tracing_agent/chrome_tracing_devtools_manager.py b/tools/telemetry/telemetry/internal/platform/tracing_agent/chrome_tracing_devtools_manager.py
new file mode 100644
index 0000000000000000000000000000000000000000..de51ea6a1ae4a61fa01dc5a6ae2766be706c8835
--- /dev/null
+++ b/tools/telemetry/telemetry/internal/platform/tracing_agent/chrome_tracing_devtools_manager.py
@@ -0,0 +1,67 @@
+# 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.
+
+class RegisterDevToolsClientError(Exception):
+  pass
+
+
+# A singleton map from platform backends to maps of uniquely-identifying
+# remote port (which may be the same as local port) to DevToolsClientBackend.
+# There is no guarantee that the devtools agent is still alive.
+_platform_backends_to_devtools_clients_maps = {}
+
+
+def _RemoveStaleDevToolsClient(platform_backend):
+  """Removes DevTools clients that are no longer connectable."""
+  devtools_clients_map = _platform_backends_to_devtools_clients_maps.get(
+      platform_backend, {})
+  devtools_clients_map = {
+      port: client
+      for port, client in devtools_clients_map.iteritems()
+      if client.IsAlive()
+      }
+  _platform_backends_to_devtools_clients_maps[platform_backend] = (
+      devtools_clients_map)
+
+
+def RegisterDevToolsClient(devtools_client_backend, platform_backend):
+  """Register DevTools client
+
+  This should only be called from DevToolsClientBackend when it is initialized.
+  """
+  if platform_backend.tracing_controller_backend.is_tracing_running:
+    raise RegisterDevToolsClientError(
+        'Cannot add new DevTools client when tracing is running on '
+        'platform backend %s.' % platform_backend)
+
+  remote_port = str(devtools_client_backend.remote_port)
+  if platform_backend not in _platform_backends_to_devtools_clients_maps:
+    _platform_backends_to_devtools_clients_maps[platform_backend] = {}
+  devtools_clients_map = (
+    _platform_backends_to_devtools_clients_maps[platform_backend])
+  devtools_clients_map[remote_port] = devtools_client_backend
+
+
+def IsSupported(platform_backend):
+  _RemoveStaleDevToolsClient(platform_backend)
+  devtools_clients_map = _platform_backends_to_devtools_clients_maps.get(
+      platform_backend, {})
+  for _, devtools_client in devtools_clients_map.iteritems():
+    if devtools_client.IsChromeTracingSupported():
+      return True
+  return False
+
+
+def GetDevToolsClients(platform_backend):
+  """Get DevTools clients including the ones that are no longer connectable."""
+  devtools_clients_map = _platform_backends_to_devtools_clients_maps.get(
+      platform_backend, {})
+  if not devtools_clients_map:
+    return []
+  return devtools_clients_map.values()
+
+def GetActiveDevToolsClients(platform_backend):
+  """Get DevTools clients that are still connectable."""
+  _RemoveStaleDevToolsClient(platform_backend)
+  return GetDevToolsClients(platform_backend)