In run_webkit_tests, use host.environ to access gtest shard env vars.

third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/run_webkit_tests.py

Index: third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/run_webkit_tests.py
diff --git a/third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/run_webkit_tests.py b/third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/run_webkit_tests.py
index 2d79e639577904c9d8911cb85907985e0286e130..ffd6dd796fa944703dc79a9328108b3b474cccee 100644
--- a/third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/run_webkit_tests.py
+++ b/third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/run_webkit_tests.py
@@ -30,7 +30,6 @@
 
 import logging
 import optparse
-import os
 import sys
 import traceback
 
@@ -543,9 +542,9 @@ def _set_up_derived_options(port, options, args):
     if not options.skipped:
         options.skipped = 'default'
 
-    if 'GTEST_SHARD_INDEX' in os.environ and 'GTEST_TOTAL_SHARDS' in os.environ:
-        shard_index = int(os.environ['GTEST_SHARD_INDEX']) + 1
-        total_shards = int(os.environ['GTEST_TOTAL_SHARDS']) + 1
+    if 'GTEST_SHARD_INDEX' in port.host.environ and 'GTEST_TOTAL_SHARDS' in port.host.environ:
+        shard_index = int(port.host.environ['GTEST_SHARD_INDEX']) + 1
+        total_shards = int(port.host.environ['GTEST_TOTAL_SHARDS']) + 1
         options.run_part = '{0}:{1}'.format(shard_index, total_shards)