[Telemetry] Add a PageTest option to clear cache before each run.

This will be used for the network simulation page cycler where we need to
ensure that each page load requests the resources from WPR instead of from
the browser cache.

BUG=None
TEST=top_25 page cycler on linux
NOTRY=True

Review URL: https://chromiumcodereview.appspot.com/16154007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@207979 0039d316-1c4b-4281-b951-d872f2087c98

tools/telemetry/docs/telemetry.core.chrome.html

@@ -46,13 +46,14 @@
 <a href="telemetry.core.chrome.inspector_console_unittest.html">inspector_console_unittest</a><br>
 <a href="telemetry.core.chrome.inspector_memory.html">inspector_memory</a><br>
 <a href="telemetry.core.chrome.inspector_memory_unittest.html">inspector_memory_unittest</a><br>
+<a href="telemetry.core.chrome.inspector_network.html">inspector_network</a><br>
 <a href="telemetry.core.chrome.inspector_page.html">inspector_page</a><br>
 <a href="telemetry.core.chrome.inspector_page_unittest.html">inspector_page_unittest</a><br>
 <a href="telemetry.core.chrome.inspector_runtime.html">inspector_runtime</a><br>
 <a href="telemetry.core.chrome.inspector_runtime_unittest.html">inspector_runtime_unittest</a><br>
 <a href="telemetry.core.chrome.inspector_timeline.html">inspector_timeline</a><br>
-<a href="telemetry.core.chrome.inspector_timeline_unittest.html">inspector_timeline_unittest</a><br>
-</td><td width="25%" valign=top><a href="telemetry.core.chrome.misc_web_contents_backend.html">misc_web_contents_backend</a><br>
+</td><td width="25%" valign=top><a href="telemetry.core.chrome.inspector_timeline_unittest.html">inspector_timeline_unittest</a><br>
+<a href="telemetry.core.chrome.misc_web_contents_backend.html">misc_web_contents_backend</a><br>
 <a href="telemetry.core.chrome.png_bitmap.html">png_bitmap</a><br>
 <a href="telemetry.core.chrome.png_bitmap_unittest.html">png_bitmap_unittest</a><br>
 <a href="telemetry.core.chrome.tab_list_backend.html">tab_list_backend</a><br>

tools/telemetry/docs/telemetry.core.chrome.inspector_backend.html

@@ -22,16 +22,17 @@
 <td width="100%"><table width="100%" summary="list"><tr><td width="25%" valign=top><a href="telemetry.core.exceptions.html">telemetry.core.exceptions</a><br>
 <a href="telemetry.core.chrome.inspector_console.html">telemetry.core.chrome.inspector_console</a><br>
 <a href="telemetry.core.chrome.inspector_memory.html">telemetry.core.chrome.inspector_memory</a><br>
-<a href="telemetry.core.chrome.inspector_page.html">telemetry.core.chrome.inspector_page</a><br>
-</td><td width="25%" valign=top><a href="telemetry.core.chrome.inspector_runtime.html">telemetry.core.chrome.inspector_runtime</a><br>
+<a href="telemetry.core.chrome.inspector_network.html">telemetry.core.chrome.inspector_network</a><br>
+</td><td width="25%" valign=top><a href="telemetry.core.chrome.inspector_page.html">telemetry.core.chrome.inspector_page</a><br>
+<a href="telemetry.core.chrome.inspector_runtime.html">telemetry.core.chrome.inspector_runtime</a><br>
 <a href="telemetry.core.chrome.inspector_timeline.html">telemetry.core.chrome.inspector_timeline</a><br>
 <a href="json.html">json</a><br>
-<a href="logging.html">logging</a><br>
-</td><td width="25%" valign=top><a href="telemetry.core.chrome.png_bitmap.html">telemetry.core.chrome.png_bitmap</a><br>
+</td><td width="25%" valign=top><a href="logging.html">logging</a><br>
+<a href="telemetry.core.chrome.png_bitmap.html">telemetry.core.chrome.png_bitmap</a><br>
 <a href="socket.html">socket</a><br>
 <a href="sys.html">sys</a><br>
-<a href="telemetry.core.util.html">telemetry.core.util</a><br>
-</td><td width="25%" valign=top><a href="telemetry.core.chrome.websocket.html">telemetry.core.chrome.websocket</a><br>
+</td><td width="25%" valign=top><a href="telemetry.core.util.html">telemetry.core.util</a><br>
+<a href="telemetry.core.chrome.websocket.html">telemetry.core.chrome.websocket</a><br>
 </td></tr></table></td></tr></table><p>
 <table width="100%" cellspacing=0 cellpadding=2 border=0 summary="section">
 <tr bgcolor="#ee77aa">
@@ -63,6 +64,8 @@
 <td width="100%">Methods defined here:<br>
 <dl><dt><a name="InspectorBackend-Activate"><strong>Activate</strong></a>(self)</dt></dl>
 
+<dl><dt><a name="InspectorBackend-ClearCache"><strong>ClearCache</strong></a>(self)</dt></dl>
+
 <dl><dt><a name="InspectorBackend-Close"><strong>Close</strong></a>(self)</dt></dl>
 
 <dl><dt><a name="InspectorBackend-CollectGarbage"><strong>CollectGarbage</strong></a>(self)</dt></dl>

tools/telemetry/docs/telemetry.core.chrome.inspector_network.html

+
+<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
+<html><head><title>Python: module telemetry.core.chrome.inspector_network</title>
+</head><body bgcolor="#f0f0f8">
+
+<table width="100%" cellspacing=0 cellpadding=2 border=0 summary="heading">
+<tr bgcolor="#7799ee">
+<td valign=bottom>&nbsp;<br>
+<font color="#ffffff" face="helvetica, arial">&nbsp;<br><big><big><strong><a href="telemetry.html"><font color="#ffffff">telemetry</font></a>.<a href="telemetry.core.html"><font color="#ffffff">core</font></a>.<a href="telemetry.core.chrome.html"><font color="#ffffff">chrome</font></a>.inspector_network</strong></big></big></font></td
+><td align=right valign=bottom
+><font color="#ffffff" face="helvetica, arial"><a href=".">index</a><br><a href="../telemetry/core/chrome/inspector_network.py">telemetry/core/chrome/inspector_network.py</a></font></td></tr></table>
+    <p><tt>#&nbsp;Copyright&nbsp;(c)&nbsp;2013&nbsp;The&nbsp;Chromium&nbsp;Authors.&nbsp;All&nbsp;rights&nbsp;reserved.<br>
+#&nbsp;Use&nbsp;of&nbsp;this&nbsp;source&nbsp;code&nbsp;is&nbsp;governed&nbsp;by&nbsp;a&nbsp;BSD-style&nbsp;license&nbsp;that&nbsp;can&nbsp;be<br>
+#&nbsp;found&nbsp;in&nbsp;the&nbsp;LICENSE&nbsp;file.</tt></p>
+<p>
+<table width="100%" cellspacing=0 cellpadding=2 border=0 summary="section">
+<tr bgcolor="#ee77aa">
+<td colspan=3 valign=bottom>&nbsp;<br>
+<font color="#ffffff" face="helvetica, arial"><big><strong>Classes</strong></big></font></td></tr>
+    
+<tr><td bgcolor="#ee77aa"><tt>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</tt></td><td>&nbsp;</td>
+<td width="100%"><dl>
+<dt><font face="helvetica, arial"><a href="__builtin__.html#object">__builtin__.object</a>
+</font></dt><dd>
+<dl>
+<dt><font face="helvetica, arial"><a href="telemetry.core.chrome.inspector_network.html#InspectorNetwork">InspectorNetwork</a>
+</font></dt></dl>
+</dd>
+</dl>
+ <p>
+<table width="100%" cellspacing=0 cellpadding=2 border=0 summary="section">
+<tr bgcolor="#ffc8d8">
+<td colspan=3 valign=bottom>&nbsp;<br>
+<font color="#000000" face="helvetica, arial"><a name="InspectorNetwork">class <strong>InspectorNetwork</strong></a>(<a href="__builtin__.html#object">__builtin__.object</a>)</font></td></tr>
+    
+<tr><td bgcolor="#ffc8d8"><tt>&nbsp;&nbsp;&nbsp;</tt></td><td>&nbsp;</td>
+<td width="100%">Methods defined here:<br>
+<dl><dt><a name="InspectorNetwork-ClearCache"><strong>ClearCache</strong></a>(self, timeout<font color="#909090">=60</font>)</dt><dd><tt>Clears&nbsp;the&nbsp;browser's&nbsp;disk&nbsp;and&nbsp;memory&nbsp;cache.</tt></dd></dl>
+
+<dl><dt><a name="InspectorNetwork-__init__"><strong>__init__</strong></a>(self, inspector_backend)</dt></dl>
+
+<hr>
+Data descriptors defined here:<br>
+<dl><dt><strong>__dict__</strong></dt>
+<dd><tt>dictionary&nbsp;for&nbsp;instance&nbsp;variables&nbsp;(if&nbsp;defined)</tt></dd>
+</dl>
+<dl><dt><strong>__weakref__</strong></dt>
+<dd><tt>list&nbsp;of&nbsp;weak&nbsp;references&nbsp;to&nbsp;the&nbsp;object&nbsp;(if&nbsp;defined)</tt></dd>
+</dl>
+</td></tr></table></td></tr></table>
+</body></html>
\ No newline at end of file

tools/telemetry/docs/telemetry.core.tab.html

@@ -69,6 +69,8 @@ and the page's documentVisibilityState becoming 'visibl
 delay&nbsp;until&nbsp;the&nbsp;actual&nbsp;tab&nbsp;is&nbsp;visible&nbsp;to&nbsp;the&nbsp;user.&nbsp;None&nbsp;of&nbsp;these&nbsp;delays<br>
 are&nbsp;included&nbsp;in&nbsp;this&nbsp;call.</tt></dd></dl>
 
+<dl><dt><a name="Tab-ClearCache"><strong>ClearCache</strong></a>(self)</dt><dd><tt>Clears&nbsp;the&nbsp;browser's&nbsp;HTTP&nbsp;disk&nbsp;cache&nbsp;and&nbsp;the&nbsp;tab's&nbsp;HTTP&nbsp;memory&nbsp;cache.</tt></dd></dl>
+
 <dl><dt><a name="Tab-CollectGarbage"><strong>CollectGarbage</strong></a>(self)</dt></dl>
 
 <dl><dt><a name="Tab-GetCookieByName"><strong>GetCookieByName</strong></a>(self, name, timeout<font color="#909090">=60</font>)</dt><dd><tt>Returns&nbsp;the&nbsp;value&nbsp;of&nbsp;the&nbsp;cookie&nbsp;by&nbsp;the&nbsp;given&nbsp;|name|.</tt></dd></dl>

tools/telemetry/docs/telemetry.html

@@ -276,7 +276,7 @@ Put&nbsp;together:<br>
 
 <dl><dt><a name="PageMeasurement-PrepareResults"><strong>PrepareResults</strong></a>(self, options)</dt></dl>
 
-<dl><dt><a name="PageMeasurement-__init__"><strong>__init__</strong></a>(self, action_name_to_run<font color="#909090">=''</font>, needs_browser_restart_after_each_run<font color="#909090">=False</font>, discard_first_result<font color="#909090">=False</font>)</dt></dl>
+<dl><dt><a name="PageMeasurement-__init__"><strong>__init__</strong></a>(self, action_name_to_run<font color="#909090">=''</font>, needs_browser_restart_after_each_run<font color="#909090">=False</font>, discard_first_result<font color="#909090">=False</font>, clear_cache_before_each_run<font color="#909090">=False</font>)</dt></dl>
 
 <hr>
 Data descriptors defined here:<br>
@@ -339,6 +339,10 @@ Data descriptors inherited from <a href="telemetry.page.page_test.html#PageTest"
 </dl>
 <dl><dt><strong>action_name_to_run</strong></dt>
 </dl>
+<dl><dt><strong>clear_cache_before_each_run</strong></dt>
+<dd><tt>When&nbsp;set&nbsp;to&nbsp;True,&nbsp;the&nbsp;browser's&nbsp;disk&nbsp;and&nbsp;memory&nbsp;cache&nbsp;will&nbsp;be&nbsp;cleared<br>
+before&nbsp;each&nbsp;run.</tt></dd>
+</dl>
 <dl><dt><strong>discard_first_result</strong></dt>
 <dd><tt>When&nbsp;set&nbsp;to&nbsp;True,&nbsp;the&nbsp;first&nbsp;run&nbsp;of&nbsp;the&nbsp;test&nbsp;is&nbsp;discarded.&nbsp;&nbsp;This&nbsp;is<br>
 useful&nbsp;for&nbsp;cases&nbsp;where&nbsp;it's&nbsp;desirable&nbsp;to&nbsp;have&nbsp;some&nbsp;test&nbsp;resource&nbsp;cached&nbsp;so<br>
@@ -378,6 +382,8 @@ and&nbsp;the&nbsp;page's&nbsp;documentVisibilityState&nbsp;becoming&nbsp;'visibl
 delay&nbsp;until&nbsp;the&nbsp;actual&nbsp;tab&nbsp;is&nbsp;visible&nbsp;to&nbsp;the&nbsp;user.&nbsp;None&nbsp;of&nbsp;these&nbsp;delays<br>
 are&nbsp;included&nbsp;in&nbsp;this&nbsp;call.</tt></dd></dl>
 
+<dl><dt><a name="Tab-ClearCache"><strong>ClearCache</strong></a>(self)</dt><dd><tt>Clears&nbsp;the&nbsp;browser's&nbsp;HTTP&nbsp;disk&nbsp;cache&nbsp;and&nbsp;the&nbsp;tab's&nbsp;HTTP&nbsp;memory&nbsp;cache.</tt></dd></dl>
+
 <dl><dt><a name="Tab-CollectGarbage"><strong>CollectGarbage</strong></a>(self)</dt></dl>
 
 <dl><dt><a name="Tab-GetCookieByName"><strong>GetCookieByName</strong></a>(self, name, timeout<font color="#909090">=60</font>)</dt><dd><tt>Returns&nbsp;the&nbsp;value&nbsp;of&nbsp;the&nbsp;cookie&nbsp;by&nbsp;the&nbsp;given&nbsp;|name|.</tt></dd></dl>

tools/telemetry/docs/telemetry.page.page_measurement.html

@@ -172,7 +172,7 @@ Put&nbsp;together:<br>
 
 <dl><dt><a name="PageMeasurement-PrepareResults"><strong>PrepareResults</strong></a>(self, options)</dt></dl>
 
-<dl><dt><a name="PageMeasurement-__init__"><strong>__init__</strong></a>(self, action_name_to_run<font color="#909090">=''</font>, needs_browser_restart_after_each_run<font color="#909090">=False</font>, discard_first_result<font color="#909090">=False</font>)</dt></dl>
+<dl><dt><a name="PageMeasurement-__init__"><strong>__init__</strong></a>(self, action_name_to_run<font color="#909090">=''</font>, needs_browser_restart_after_each_run<font color="#909090">=False</font>, discard_first_result<font color="#909090">=False</font>, clear_cache_before_each_run<font color="#909090">=False</font>)</dt></dl>
 
 <hr>
 Data descriptors defined here:<br>
@@ -235,6 +235,10 @@ Data descriptors inherited from <a href="telemetry.page.page_test.html#PageTest"
 </dl>
 <dl><dt><strong>action_name_to_run</strong></dt>
 </dl>
+<dl><dt><strong>clear_cache_before_each_run</strong></dt>
+<dd><tt>When&nbsp;set&nbsp;to&nbsp;True,&nbsp;the&nbsp;browser's&nbsp;disk&nbsp;and&nbsp;memory&nbsp;cache&nbsp;will&nbsp;be&nbsp;cleared<br>
+before&nbsp;each&nbsp;run.</tt></dd>
+</dl>
 <dl><dt><strong>discard_first_result</strong></dt>
 <dd><tt>When&nbsp;set&nbsp;to&nbsp;True,&nbsp;the&nbsp;first&nbsp;run&nbsp;of&nbsp;the&nbsp;test&nbsp;is&nbsp;discarded.&nbsp;&nbsp;This&nbsp;is<br>
 useful&nbsp;for&nbsp;cases&nbsp;where&nbsp;it's&nbsp;desirable&nbsp;to&nbsp;have&nbsp;some&nbsp;test&nbsp;resource&nbsp;cached&nbsp;so<br>

tools/telemetry/docs/telemetry.page.page_test.html

@@ -158,7 +158,7 @@ is&nbsp;torn&nbsp;down.</tt></dd></dl>
 
 <dl><dt><a name="PageTest-WillRunPageSet"><strong>WillRunPageSet</strong></a>(self, tab)</dt><dd><tt>Override&nbsp;to&nbsp;do&nbsp;operations&nbsp;before&nbsp;the&nbsp;page&nbsp;set&nbsp;is&nbsp;navigated.</tt></dd></dl>
 
-<dl><dt><a name="PageTest-__init__"><strong>__init__</strong></a>(self, test_method_name, action_name_to_run<font color="#909090">=''</font>, needs_browser_restart_after_each_run<font color="#909090">=False</font>, discard_first_result<font color="#909090">=False</font>)</dt></dl>
+<dl><dt><a name="PageTest-__init__"><strong>__init__</strong></a>(self, test_method_name, action_name_to_run<font color="#909090">=''</font>, needs_browser_restart_after_each_run<font color="#909090">=False</font>, discard_first_result<font color="#909090">=False</font>, clear_cache_before_each_run<font color="#909090">=False</font>)</dt></dl>
 
 <hr>
 Data descriptors defined here:<br>
@@ -170,6 +170,10 @@ Data descriptors defined here:<br>
 </dl>
 <dl><dt><strong>action_name_to_run</strong></dt>
 </dl>
+<dl><dt><strong>clear_cache_before_each_run</strong></dt>
+<dd><tt>When&nbsp;set&nbsp;to&nbsp;True,&nbsp;the&nbsp;browser's&nbsp;disk&nbsp;and&nbsp;memory&nbsp;cache&nbsp;will&nbsp;be&nbsp;cleared<br>
+before&nbsp;each&nbsp;run.</tt></dd>
+</dl>
 <dl><dt><strong>discard_first_result</strong></dt>
 <dd><tt>When&nbsp;set&nbsp;to&nbsp;True,&nbsp;the&nbsp;first&nbsp;run&nbsp;of&nbsp;the&nbsp;test&nbsp;is&nbsp;discarded.&nbsp;&nbsp;This&nbsp;is<br>
 useful&nbsp;for&nbsp;cases&nbsp;where&nbsp;it's&nbsp;desirable&nbsp;to&nbsp;have&nbsp;some&nbsp;test&nbsp;resource&nbsp;cached&nbsp;so<br>

tools/telemetry/docs/telemetry.page.page_test_runner.html

@@ -100,5 +100,12 @@ Data descriptors defined here:<br>
 &nbsp;<br>
 Args:<br>
 &nbsp;&nbsp;base_dir:&nbsp;Path&nbsp;to&nbsp;directory&nbsp;containing&nbsp;tests&nbsp;and&nbsp;ProfileCreators.</tt></dd></dl>
-</td></tr></table>
+</td></tr></table><p>
+<table width="100%" cellspacing=0 cellpadding=2 border=0 summary="section">
+<tr bgcolor="#55aa55">
+<td colspan=3 valign=bottom>&nbsp;<br>
+<font color="#ffffff" face="helvetica, arial"><big><strong>Data</strong></big></font></td></tr>
+    
+<tr><td bgcolor="#55aa55"><tt>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</tt></td><td>&nbsp;</td>
+<td width="100%"><strong>__warningregistry__</strong> = {("Not importing directory '/usr/local/google/code/...ls/telemetry/telemetry/test': missing __init__.py", &lt;type 'exceptions.ImportWarning'&gt;, 7): True}</td></tr></table>
 </body></html>
\ No newline at end of file

tools/telemetry/docs/telemetry.page.record_wpr.html

@@ -115,6 +115,10 @@ Data descriptors inherited from <a href="telemetry.page.page_test.html#PageTest"
 </dl>
 <dl><dt><strong>action_name_to_run</strong></dt>
 </dl>
+<dl><dt><strong>clear_cache_before_each_run</strong></dt>
+<dd><tt>When&nbsp;set&nbsp;to&nbsp;True,&nbsp;the&nbsp;browser's&nbsp;disk&nbsp;and&nbsp;memory&nbsp;cache&nbsp;will&nbsp;be&nbsp;cleared<br>
+before&nbsp;each&nbsp;run.</tt></dd>
+</dl>
 <dl><dt><strong>discard_first_result</strong></dt>
 <dd><tt>When&nbsp;set&nbsp;to&nbsp;True,&nbsp;the&nbsp;first&nbsp;run&nbsp;of&nbsp;the&nbsp;test&nbsp;is&nbsp;discarded.&nbsp;&nbsp;This&nbsp;is<br>
 useful&nbsp;for&nbsp;cases&nbsp;where&nbsp;it's&nbsp;desirable&nbsp;to&nbsp;have&nbsp;some&nbsp;test&nbsp;resource&nbsp;cached&nbsp;so<br>

tools/telemetry/telemetry/core/chrome/inspector_backend.py

@@ -10,6 +10,7 @@ from telemetry.core import util
 from telemetry.core import exceptions
 from telemetry.core.chrome import inspector_console
 from telemetry.core.chrome import inspector_memory
+from telemetry.core.chrome import inspector_network
 from telemetry.core.chrome import inspector_page
 from telemetry.core.chrome import inspector_runtime
 from telemetry.core.chrome import inspector_timeline
@@ -35,6 +36,7 @@ class InspectorBackend(object):
     self._page = inspector_page.InspectorPage(self)
     self._runtime = inspector_runtime.InspectorRuntime(self)
     self._timeline = inspector_timeline.InspectorTimeline(self)
+    self._network = inspector_network.InspectorNetwork(self)
 
   def __del__(self):
     self.Disconnect()
@@ -199,6 +201,11 @@ class InspectorBackend(object):
   def StopTimelineRecording(self):
     self._timeline.Stop()
 
+  # Network public methods.
+
+  def ClearCache(self):
+    self._network.ClearCache()
+
   # Methods used internally by other backends.
 
   def DispatchNotifications(self, timeout=10):

tools/telemetry/telemetry/core/chrome/inspector_network.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.
+
+class InspectorNetwork(object):
+  def __init__(self, inspector_backend):
+    self._inspector_backend = inspector_backend
+
+  def ClearCache(self, timeout=60):
+    """Clears the browser's disk and memory cache."""
+    res = self._inspector_backend.SyncRequest({
+        'method': 'Network.canClearBrowserCache'
+        }, timeout)
+    assert res['result'], 'Cache clearing is not supported by this browser'
+    self._inspector_backend.SyncRequest({
+        'method': 'Network.clearBrowserCache'
+        }, timeout)

tools/telemetry/telemetry/core/tab.py

@@ -98,3 +98,7 @@ class Tab(web_contents.WebContents):
 
   def CollectGarbage(self):
     self._inspector_backend.CollectGarbage()
+
+  def ClearCache(self):
+    """Clears the browser's HTTP disk cache and the tab's HTTP memory cache."""
+    self._inspector_backend.ClearCache()

tools/telemetry/telemetry/page/page_measurement.py

@@ -44,12 +44,14 @@ class PageMeasurement(page_test.PageTest):
   def __init__(self,
                action_name_to_run='',
                needs_browser_restart_after_each_run=False,
-               discard_first_result=False):
+               discard_first_result=False,
+               clear_cache_before_each_run=False):
     super(PageMeasurement, self).__init__(
       '_RunTest',
       action_name_to_run,
       needs_browser_restart_after_each_run,
-      discard_first_result)
+      discard_first_result,
+      clear_cache_before_each_run)
 
   def _RunTest(self, page, tab, results):
     results.WillMeasurePage(page)

tools/telemetry/telemetry/page/page_runner.py

@@ -143,6 +143,8 @@ class PageState(object):
       self._did_login = True
 
     if test:
+      if test.clear_cache_before_each_run:
+        tab.ClearCache()
       test.WillNavigateToPage(page, tab)
     tab.Navigate(target_side_url, page.script_to_evaluate_on_commit)
     if test:

tools/telemetry/telemetry/page/page_test.py

@@ -49,7 +49,8 @@ class PageTest(object):
                test_method_name,
                action_name_to_run='',
                needs_browser_restart_after_each_run=False,
-               discard_first_result=False):
+               discard_first_result=False,
+               clear_cache_before_each_run=False):
     self.options = None
     try:
       self._test_method = getattr(self, test_method_name)
@@ -60,6 +61,7 @@ class PageTest(object):
     self._needs_browser_restart_after_each_run = (
         needs_browser_restart_after_each_run)
     self._discard_first_result = discard_first_result
+    self._clear_cache_before_each_run = clear_cache_before_each_run
 
   @property
   def discard_first_result(self):
@@ -68,6 +70,12 @@ class PageTest(object):
     the first run of the test can warm things up. """
     return self._discard_first_result
 
+  @property
+  def clear_cache_before_each_run(self):
+    """When set to True, the browser's disk and memory cache will be cleared
+    before each run."""
+    return self._clear_cache_before_each_run
+
   def NeedsBrowserRestartAfterEachRun(self, tab): # pylint: disable=W0613
     """Override to specify browser restart after each run."""
     return self._needs_browser_restart_after_each_run