Do not override CHROME_DEVEL_SANDBOX in tools/valgrind/valgrind_test.py

Setting that variable to an empty string is not a supported way of disabling the
sandbox. tools/valgrind/chrome_tests.py is supposed to pass "--no-sandbox" which
takes care of that.

BUG=245376
TBR=jln@chromium.org, timurrrr@chromium.org
NOTRY=true

Review URL: https://codereview.chromium.org/880023003

Cr-Commit-Position: refs/heads/master@{#313517}

tools/valgrind/valgrind_test.py

@@ -380,12 +380,6 @@ class ValgrindTool(BaseTool):
 
     # 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|.