Revert "Modernize SkMutex and SkSemaphore."

src/lazy/SkDiscardableMemoryPool.h

Index: src/lazy/SkDiscardableMemoryPool.h
diff --git a/src/lazy/SkDiscardableMemoryPool.h b/src/lazy/SkDiscardableMemoryPool.h
index ad8d796f664b9f2e502dfdab8e97c645374a545e..92ba48bcb492fb3f50bd50ea2143ad5016fbc676 100644
--- a/src/lazy/SkDiscardableMemoryPool.h
+++ b/src/lazy/SkDiscardableMemoryPool.h
@@ -52,7 +52,8 @@ public:
      *  the pool works.
      *  Without mutex, will be not be thread safe.
      */
-    static SkDiscardableMemoryPool* Create(size_t size, SkMutex* mutex = nullptr);
+    static SkDiscardableMemoryPool* Create(
+            size_t size, SkBaseMutex* mutex = nullptr);
 };
 
 /**