smoothness.scrolling_tough_ad_cases to use browser driven scrolls

tools/telemetry/telemetry/internal/backends/chrome_inspector/inspector_backend.py

Index: tools/telemetry/telemetry/internal/backends/chrome_inspector/inspector_backend.py
diff --git a/tools/telemetry/telemetry/internal/backends/chrome_inspector/inspector_backend.py b/tools/telemetry/telemetry/internal/backends/chrome_inspector/inspector_backend.py
index 3aa050a1f6f31bf9186167fe66fbde5f5e373fc5..d6fb86db9b6054e3fd764e19aa38bd450da0a46d 100644
--- a/tools/telemetry/telemetry/internal/backends/chrome_inspector/inspector_backend.py
+++ b/tools/telemetry/telemetry/internal/backends/chrome_inspector/inspector_backend.py
@@ -223,6 +223,17 @@ class InspectorBackend(object):
     """
     return self._runtime.EnableAllContexts()
 
+  @_HandleInspectorWebSocketExceptions
+  def RunInspectorCommand(self, command, timeout=60):

[Sami, 2015/08/17 17:06:44]

It feels like this is a too level interface to be exposing here. How about we
model this after, say, Screenshot(), and call it something like
SynthesizeScrollGesture() and have a synthesize_scroll_gesture_supported
property? Remember we need to check for support anyway since telemetry might be
running against an older version of Chrome.

[alex clarke (OOO till 29th), 2015/08/18 13:40:51]

Done.

+    """Runs an inspector command.
+
+    Raises:
+      exceptions.WebSocketDisconnected
+      exceptions.TimeoutException
+      exceptions.DevtoolsTargetCrashException
+    """
+    return self._runtime.RunInspectorCommand(command, timeout)
+
   # Timeline public methods.
 
   @property