[telemetry] Add support for requesting memory dumps via DevTools API

tools/telemetry/telemetry/internal/backends/browser_backend.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.
 
 from telemetry.core import platform
 from telemetry import decorators
 from telemetry.internal.backends import app_backend
 from telemetry.internal.browser import web_contents
 from telemetry.internal.platform import profiling_controller_backend
 
@@ skipping 83 matching lines @@
     return self.IsBrowserRunning()
 
   def GetStandardOutput(self):
     raise NotImplementedError()
 
   def GetStackTrace(self):
     raise NotImplementedError()
 
   def GetSystemInfo(self):
     raise NotImplementedError()
+
+  @property
+  def supports_memory_dumping(self):
+    return False
+
+  def DumpMemory(self, timeout=web_contents.DEFAULT_WEB_CONTENTS_TIMEOUT):
+    raise NotImplementedError()