Exclude SerialApiTests on DrMemory.

They don't seem to work there now that they use mojo. See referenced bug
for details.

TBR=zhaoqin@chromium.org
BUG=372452
NOTRY=true

Review URL: https://codereview.chromium.org/698913003

Cr-Commit-Position: refs/heads/master@{#302569}

tools/valgrind/gtest_exclude/browser_tests.gtest-drmemory_win32.txt

@@ -160,6 +160,8 @@ Req*.Per*ion
 # S*
 Sa*
 Sea*Pr*
+# SerialApiTest.SerialFakeHardware_1 (http://crbug.com/372452)
+Ser*
 Ses*
 Set*
 Scr*