Revert of Remove chrome_app_unittests from chromium_builder_dbg_drmem…

…ory_win target (patchset chromium#1 id:1 of https://codereview.chromium.org/2286623002/ )

Reason for revert:
Reverting, because Dr. Memory test bots need that executable. It didn't break until a clobber landed and deleted the executable generated in the past.

Also glider@ reports that chrome_app_unittests was probably innocent (in the bug report) anyways.

First breaking build: https://build.chromium.org/p/chromium.memory.full/builders/Windows%20Unit%20%28DrMemory%20full%29%20%285%29/builds/130

Original issue's description:
> Remove chrome_app_unittests from chromium_builder_dbg_drmemory_win target
>
> This should probably fix the compile step on the Dr. Memory builder.
>
> BUG=640185
> TBR=dpranke@chromium.org,cpu@chromium.org
> NOTRY=true
>
> Committed: https://crrev.com/48586ee56e601e60095f30723060d4bd888ce6fe
> Cr-Commit-Position: refs/heads/master@{#414670}

TBR=cpu@chromium.org,dpranke@chromium.org,glider@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=640185

Review-Url: https://codereview.chromium.org/2341353002
Cr-Commit-Position: refs/heads/master@{#419219}

BUILD.gn

@@ -1082,9 +1082,7 @@ if (is_win) {
       "//chrome/installer/setup:setup_unittests",
       "//chrome/installer/util:installer_util_unittests",
       "//chrome/test:browser_tests",
-
-      # https://crbug.com/640185
-      # "//chrome/test:chrome_app_unittests",
+      "//chrome/test:chrome_app_unittests",
       "//chrome/test:unit_tests",
       "//chrome/test/chromedriver:chromedriver_unittests",
       "//chrome_elf:chrome_elf_unittests",