Pass False for fromSurface argument to Page.captureScreenshot.

telemetry/telemetry/internal/backends/chrome_inspector/inspector_page.py

 # Copyright 2013 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.
 import time
 
 from telemetry.util import image_util
 
 
 class InspectorPage(object):
   """Class that controls a page connected by an inspector_websocket.
@@ skipping 120 matching lines @@
         }
     res = self._inspector_websocket.SyncRequest(request, timeout)
     cookies = res['result']['cookies']
     for cookie in cookies:
       if cookie['name'] == name:
         return cookie['value']
     return None
 
   def CaptureScreenshot(self, timeout=60):
     request = {
-        'method': 'Page.captureScreenshot'
+        'method': 'Page.captureScreenshot',
+        # TODO(rmistry): when Chrome is running in headless mode, this
+        # will need to pass True. Telemetry needs to understand
+        # whether the browser is in headless mode, and pass that
+        # knowledge down to this method.
+        'fromSurface': False
         }
     # "Google API are missing..." infobar might cause a viewport resize
     # which invalidates screenshot request. See crbug.com/459820.
     for _ in range(2):
       res = self._inspector_websocket.SyncRequest(request, timeout)
       if res and ('result' in res) and ('data' in res['result']):
         return image_util.FromBase64Png(res['result']['data'])
     return None
 
   def CollectGarbage(self, timeout=60):
     request = {
         'method': 'HeapProfiler.collectGarbage'
         }
     res = self._inspector_websocket.SyncRequest(request, timeout)
     assert 'result' in res