Introduce TracingController and TracingControllerBackend skeleton

tools/telemetry/telemetry/core/platform/__init__.py

Index: tools/telemetry/telemetry/core/platform/__init__.py
diff --git a/tools/telemetry/telemetry/core/platform/__init__.py b/tools/telemetry/telemetry/core/platform/__init__.py
index a13cbc279de200ee51938e94b511a4c68f231888..90570b38914f6801a40df8185f7c8aff336718b5 100644
--- a/tools/telemetry/telemetry/core/platform/__init__.py
+++ b/tools/telemetry/telemetry/core/platform/__init__.py
@@ -4,6 +4,8 @@
 
 import sys
 
+from telemetry.core.platform import tracing_controller
+
 
 _host_platform = None
 
@@ -43,6 +45,12 @@ class Platform(object):
   def __init__(self, platform_backend):
     self._platform_backend = platform_backend
     self._platform_backend.SetPlatform(self)
+    self._tracing_controller = tracing_controller.TracingController(
+        self._platform_backend.tracing_controller_backend)
+
+  @property
+  def tracing_controller(self):
+    return self._tracing_controller
 
   def IsRawDisplayFrameRateSupported(self):
     """Platforms may be able to collect GL surface stats."""