[tools/perf] Delete unused variable

tools/perf/measurements/image_decoding.py

 # Copyright 2012 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.page import page_test
 from telemetry.timeline import model
 from telemetry.timeline import tracing_config
 from telemetry.value import scalar
 
 from metrics import power
@@ skipping 30 matching lines @@
     # FIXME: Remove the devtools.timeline category when impl-side painting is
     # on everywhere.
     config.tracing_category_filter.AddDisabledByDefault(
         'disabled-by-default-devtools.timeline')
     for c in ['blink', 'devtools.timeline', 'webkit.console', 'blink.console']:
       config.tracing_category_filter.AddIncludedCategory(c)
     config.enable_chrome_trace = True
     tab.browser.platform.tracing_controller.StartTracing(config)
 
   def StopBrowserAfterPage(self, browser, page):
+    del page  # unused
     return not browser.tabs[0].ExecuteJavaScript("""
         window.chrome &&
             chrome.gpuBenchmarking &&
             chrome.gpuBenchmarking.clearImageCache;
     """)
 
   def ValidateAndMeasurePage(self, page, tab, results):
     timeline_data = tab.browser.platform.tracing_controller.StopTracing()
     timeline_model = model.TimelineModel(timeline_data)
     self._power_metric.Stop(page, tab)
@@ skipping 29 matching lines @@
                     'formats: gif, png, jpg, and webp. The image files are '
                     'located at chrome/test/data/image_decoding.'))
     results.AddValue(scalar.ScalarValue(
         results.current_page, 'ImageLoading_avg', 'ms',
         tab.EvaluateJavaScript('averageLoadingTimeMs()')))
 
   def DidRunPage(self, platform):
     self._power_metric.Close()
     if platform.tracing_controller.is_tracing_running:
       platform.tracing_controller.StopTracing()