Make timeline model able to return browser process

tools/telemetry/telemetry/core/timeline/model.py

Index: tools/telemetry/telemetry/core/timeline/model.py
diff --git a/tools/telemetry/telemetry/core/timeline/model.py b/tools/telemetry/telemetry/core/timeline/model.py
index ec8dccb4b786b19c605dbbac5dad2898bb4e9fb1..3ca2e7db8a90a442c2fe4e93c132875d4d94267b 100644
--- a/tools/telemetry/telemetry/core/timeline/model.py
+++ b/tools/telemetry/telemetry/core/timeline/model.py
@@ -42,6 +42,7 @@ class TimelineModel(object):
     self._bounds = bounds.Bounds()
     self._thread_time_bounds = {}
     self._processes = {}
+    self._browser_process = None
     self._frozen = False
     self.import_errors = []
     self.metadata = []
@@ -65,6 +66,14 @@ class TimelineModel(object):
   def processes(self):
     return self._processes
 
+  @property
+  def browser_process(self):
+    return self._browser_process
+
+  @browser_process.setter
+  def browser_process(self, browser_process):
+    self._browser_process = browser_process
+
   def ImportTraces(self, traces, shift_world_to_zero=True):
     if self._frozen:
       raise Exception("Cannot add events once recording is done")