Revert 146303 - Disables allocator_shim on Windows memory builders.

Revert 146303 - Disables allocator_shim on Windows memory builders.
This change disables allocator_shim on Windows memory builders because it causes a linker error with the latest ANGLE code as reported by Erik (*1). Allocator_shim is disabled on shared builds and it happens only on memory builders, which use static builds. (All the other Windows debug builders use shared builds.)

(*1) https://groups.google.com/a/chromium.org/group/chromium-dev/browse_thread/thread/4197e93c6f5814ef/330ea8d9d31141e1?lnk=gst&q=base%2Fallocator+#330ea8d9d31141e1

BUG=none
TEST=build unit_tests.exe on the "Windows Tests (tsan)" bot and the "Chromium Windows Builder (DrMemory)" bot.
Review URL: https://chromiumcodereview.appspot.com/10704178

TBR=hbono@chromium.org
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=146487