Fix componene debug build failure in chromium

The error log is as follows:
../../third_party/skia/include/core/SkSpinlock.h:24: error: undefined reference to 'SkPODSpinlock::contendedAcquire()'
collect2: error: ld returned 1 exit status

[mtklein added below here]
Despite the presence in include/ and the added SK_API, this file is not part of Skia's public API... it's just used by files which are.
TBR=reed@google.com

Review URL: https://codereview.chromium.org/1229003004
1 file changed