Workaround for glibc semaphore bug.

src/base/platform/semaphore.h

Index: src/base/platform/semaphore.h
diff --git a/src/base/platform/semaphore.h b/src/base/platform/semaphore.h
index ad8c7ec68be9f100acd1064bc6e40734a73c233c..18700d1ba005f01a77a2fb43f7c6b3219200f382 100644
--- a/src/base/platform/semaphore.h
+++ b/src/base/platform/semaphore.h
@@ -37,8 +37,7 @@ class Semaphore final {
   ~Semaphore();
 
   // Increments the semaphore counter.
-  // TODO(ulan): remove caller parameter once crbug.com/609249 is fixed.
-  void Signal(const char* caller = nullptr);
+  void Signal();
 
   // Suspends the calling thread until the semaphore counter is non zero
   // and then decrements the semaphore counter.