Update from https://crrev.com/314320

tools/valgrind/valgrind_test.py

 # Copyright (c) 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.
 
 """Runs an exe through Valgrind and puts the intermediate files in a
 directory.
 """
 
 import datetime
 import glob
@@ skipping 362 matching lines @@
       logging.warning("WARNING: NOT USING SUPPRESSIONS!")
 
     logfilename = self.log_dir + ("/%s." % tool_name) + "%p"
     if self.UseXML():
       proc += ["--xml=yes", "--xml-file=" + logfilename]
     else:
       proc += ["--log-file=" + logfilename]
 
     # The Valgrind command is constructed.
 
-    # Valgrind doesn't play nice with the Chrome sandbox.  Empty this env var
-    # set by runtest.py to disable the sandbox.
-    if os.environ.get("CHROME_DEVEL_SANDBOX", None):
-      logging.info("Removing CHROME_DEVEL_SANDBOX from environment")
-      os.environ["CHROME_DEVEL_SANDBOX"] = ''
-
     # Handle --indirect_webkit_layout separately.
     if self._options.indirect_webkit_layout:
       # Need to create the wrapper before modifying |proc|.
       wrapper = self.CreateBrowserWrapper(proc, webkit=True)
       proc = self._args
       proc.append("--wrapper")
       proc.append(wrapper)
       return proc
 
     if self._options.indirect:
@@ skipping 312 matching lines @@
 
     # Un-comment to disable interleaved output.  Will also suppress error
     # messages normally printed to stderr.
     #proc += ["-quiet", "-no_results_to_stderr"]
 
     proc += ["-callstack_max_frames", "40"]
 
     # disable leak scan for now
     proc += ["-no_count_leaks", "-no_leak_scan"]
 
+    # disable warnings about unaddressable prefetches
+    proc += ["-no_check_prefetch"]
+
     # crbug.com/413215, no heap mismatch check for Windows release build binary
     if common.IsWindows() and "Release" in self._options.build_dir:
         proc += ["-no_check_delete_mismatch"]
 
     # make callstacks easier to read
     proc += ["-callstack_srcfile_prefix",
              "build\\src,chromium\\src,crt_build\\self_x86"]
     proc += ["-callstack_modname_hide",
              "*drmemory*,chrome.dll"]
 
@@ skipping 97 matching lines @@
       return DrMemory(False, True)
     try:
       platform_name = common.PlatformNames()[0]
     except common.NotImplementedError:
       platform_name = sys.platform + "(Unknown)"
     raise RuntimeError, "Unknown tool (tool=%s, platform=%s)" % (tool_name,
                                                                  platform_name)
 
 def CreateTool(tool):
   return ToolFactory().Create(tool)