Support //chrome/test:unit_tests in autotest.py

Bug: 1066521
Change-Id: Ib591b5ee471f4bc55a8fbbec2a1cd0b4762e1b60
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2129990Reviewed-by: Brandon Wylie <wylieb@chromium.org>
Commit-Queue: Michael Thiessen <mthiesse@chromium.org>
Cr-Commit-Position: refs/heads/master@{#754994}

tools/autotest.py

@@ -39,8 +39,11 @@ _TEST_TARGET_SUFFIXES = [
     '_unittests',
 ]
 
+# Some test suites use suffixes that would also match non-test-suite targets.
+# Those test suites should be manually added here.
 _OTHER_TEST_TARGETS = [
     '//chrome/test:browser_tests',
+    '//chrome/test:unit_tests',
 ]